Could Dengue Spread in a Warming World?

Guest Essay by Kip Hansen

featured_image_dengueA new paper in nature microbiology makes the following statement:

Dengue is a mosquito-borne viral infection that has spread throughout the tropical world over the past 60 years and now affects over half the world’s population. The geographical range of dengue is expected to further expand due to ongoing global phenomena including climate change and urbanization.”

 The paper, “The current and future global distribution and population at risk of dengue” [Messina2019 ] is open source and available as a .pdf here.  As required by the Editorial Narrative of the NY Times regarding all things climatic, our ever-hard-working NY Times journalist, Kendra Pierre-Louis, was tasked with spreading the gloom.

If you don’t know what Dengue Fever is you obviously have not traveled to the Caribbean or South or Central America recently, where dengue is endemic and epidemic.

“Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. This may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash.  Recovery generally takes two to seven days. In a small proportion of cases, the disease develops into severe dengue, also known as dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs.” —  Wiki

Like malaria, dengue is transmitted by mosquitoes, but the mosquitoes each individually need to obtain the virus by biting an infected human before they can pass dengue on to an uninfected human by biting them.   Thus, two things are necessary for the occurrence of dengue fever in a human population:  a widespread population of mosquitoes (typically  Aedes aegypti) and infected humans.  Note that Aedes mosquitoes can only fly about 100 meters in the wild, so suitable breeding sites have to be ubiquitous in the environment and many infected human hosts have to be present and live close together.  This is why dengue has such prevalence in the tropical third world.

Further, Aedes aegypti prefer to breed in very small bodies of water — such as the rain water collected in a discarded car tire or a tin can  and often in the rain barrels common in communities that do not have reliable municipal water systems.

In the Domincan Republic, where my wife and I recently worked for a humanitarian NGO, dengue is rampant — both endemic (said of a disease or condition that is regularly found among particular people or in a certain area) and epidemic (an instance of widespread occurrence of an infectious disease in a community at a particular time). (see maps below)   This just means that it is commonly found among the people there, and that, sometimes, some city or region will experience an outbreak that effects a significant percentage of the population.

Personal Experience:  While we were serving there, the largest city on the northern coast had a dengue epidemic which had been ongoing for a couple of months.  The regional health minister contacted us with a plea for help (we had worked with him on some local health clinic projects).  When we asked what they had done in the past for these outbreaks, he explained that the health department would go to the local “all-inclusive resort” (owned and operated by international corporations) and borrow their anti-mosquito spraying equipment.  In this case though, the epidemic was so wide-spread that the resort had its equipment in almost full-time use to ensure that none of their American or European guests contracted dengue.  We arranged for the organization that we worked for to purchase a powerful aerosol  sprayer that could be mounted in the back of a small pickup (that could easily pass through the narrow streets) and two backpack sprayers (think Ghost Busters) to go into the narrow alleyways between homes.  Spraying along with community efforts to remove all mosquito breeding sites (trash, tires, tin cans) and to cover water barrels with cloth tops stopped the epidemic within a week.  The availability of community-owned vector control equipment (sprayers) resulted in a long term improvement in dengue control in this city.    Dengue was and is still present there, due to the mobility of infected individuals and the mobility of Aedes aegypti due to transportation of goods and materials from around the country, resulting in their re-introduction to the city. But its incidence has been reduced below epidemic levels.

backpack_sprayersBackpack sprayers, which look oddly like those featured in Ghost Busters, are very effective in knocking down mosquito populations in crowded cities with their narrow alleyways between and behind houses.

Dengue needs lots of people crammed into small areas with plentiful breeding sites — small warm bodies of water.  This describes almost all the poorer sections of all Developing World (3rd World) countries in the tropical regions of the planet.


This map shows malaria in the top half — we can see that malaria has been more or less confined to central Africa, with lower risk areas in the north of South America and throughout India and Southeast Asia.  Malaria has been more or less eliminated from North America and Europe – and has never been a real problem in dry, desert areas.  Dengue has a different, though similar, distribution,   although again Central Africa, India and SE Asia are potential hot spots as this map is of “suitable” environment.

This next map gives a bit  more informative view:


from Bhatt el al. 2013, in Nature “The global distribution and burden of dengue”.Click here for full sized image.

(Note:  the bottom global map in the image was distorted in the original.)

The three global views in this image are of different things and the colors do not represent the same ideas.  The top map shows “evidence consensus” (how sure are we that dengue exists in this nation or does not exist).  The second show how probably it is that dengue exists (0 to 1) in 5 km grids sections.  The bottom (distorted) map shows “number of infections” which depends on reliability of reporting.

Now that we have some idea of where dengue is found now, and WHY it is found there, let’s see what Messina et al. (2019) are projecting:


Now, let’s see what they are trying to show in this map. “Under a moderate warming scenario, 2.5 billion more people could be at risk for dengue fever by 2080.” The darker colors represent “higher dengue risk” than in 2015.   The authors claim to have “modeled”  the future of dengue as follows (serious readers can skip their description):

Dengue future modelling ensemble approach. Our final aim was to produce nine maps, a prediction for dengue suitability in the years 2020, 2050 and 2080 under three different emissions scenarios (RCPs). Each of these nine maps were composed of 100 ensemble predictions that randomly sampled (with replacement) the  following aspects of the analysis:

  1. The fitted dengue BRT [ensemble boosted regression tree] model (from a choice of 100 BRT models fitted to 2015 data).
  2. The predicted future distribution of Ae. aegypti (from a choice of 100 modelpredictions).
  3. The predicted future distribution of Ae. albopictus (from a choice of 100 model predictions).
  4. The predicted temperature suitability for dengue transmission (from a choiceof 17 GCMs).
  5. The predicted minimum monthly precipitation (from a choice of 17 GCMs)
  6. The predicted relative humidity (from a choice of 17 GCMs).
  7. The predicted maximum monthly precipitation (from a choice of 17 GCMs).

This approach sought to fully propagate the uncertainty in the climate, Aedes and dengue models through to the final prediction (see maps of uncertainty estimates in Supplementary Fig. 5). These 100 predictions were then summarized by mean and 95% credible intervals to give the final prediction for each year RCP combination.

This approach is so fraught with problems that I don’t know where to start.  But biological and historical plausibility is a good place to start.  Is the distribution of Ae. Aegypti mosquitoes, and thus dengue,  primarily temperature dependent?

The answer to that is NO and YES.  Ae. Aegypt cannot survive in deserts with extremely low humidity, they cannot survive where temperatures get too cold in winter, thus there is a lower temperature climatic limit, but according to the CDC, they already  can and do survive in much of the United States, as of 2017:


But when we look at the map of where dengue is found today, first map in this essay, we find it is not simply found where Ae. Aegypti are currently found, as the map of the United States shows.  Why not?  Because the existence of dengue in any particular place depends on much more than simply the (possible) existence of its primary insect vector.  Note that the same is true for malaria — the mosquitoes are here (in reduced numbers due to controls) but malaria is not.

Ae Aegypti  mosquitoes are the primary insect vector for both dengue and yellow fever — by looking at the historical records for yellow fever we have a proxy for dengue (which was confined to SE Asia before World War II).  Even in the depths of the Little Ice Age,  yellow fever was present and killing people as far north as Boston in the 1600s-1800s.  Should we expect a modern epidemic of dengue in Boston?  Of course not.


Why? Because:

“….the mosquito vectors capable of transmitting malaria, yellow fever, and dengue have been present throughout much of the United States since the 1600s. What has clearly changed in the United States from the 18th and 19th centuries to the present is the availability of potable water, sanitation, and social lifestyles. These developments have essentially eliminated the need to store water in indoor containers and reduced contact with mosquitoes. After World War II, and particularly during the 1950s, a boom in the US economy increased the standard of living and aided the widespread use of television and air conditioning. In addition, the use of screened terraces and windows increased.”…”Thus, diseases such as malaria, yellow fe­ver, and dengue have all but disappeared.”

The Messina et al. projections of dengue risk in the American south and in the desert areas of southern Arizona and New Mexico are not biologically plausible when one takes into account current living standards and modern vector control efforts already extant in these areas.  Northern Australia is another area that is unlikely to be plagued by mosquito borne disease.

As for Africa, India, China, and SE Asia, as population increases and concentrates in cities, the poor will live in slums, rife for dengue, and incidence of dengue will rise proportionally.   But as  these developing countries advance and standards rise to include screened windows, air conditioning, and sanitation — there will be less risk of mosquito-spread diseases.  As health standards rise, there will be fewer infected individuals being bitten by mosquitoes thus less transmission of these diseases.

The Bottom Line:

 1.  Dengue is a mosquito borne disease that depends on poor sanitation and non-existent vector control to remain a problem in areas where it is endemic. It can be eliminated, just like yellow fever and malaria were eliminated in the United States.

 2.  Raising standards of living high enough to allow homes to be protected with screened windows, screen doors, municipal water (with pipes) and to have reliable functioning trash collection will eliminate much of the dengue load in a country.

 3.  Public health programs that inform the population of risks and instruct them to eliminate breeding spots for mosquitoes, along with serious vector control (spraying)  reduces risk.

 4.  Where dengue is endemic and epidemic, it is a real ongoing public health problem and should not be ignored or brushed off, even if this new paper exaggerates the increasing risks — in some countries it is just a fact of life taking children and the elderly to their graves.

 5.  It is unreasonable to maintain that as these developing countries advance that they will not achieve the two items (2 and 3) above….international aid programs can help in this regard and will do much more to protect the health of people  than any of the climate change initiatives being pushed by political activists.

6.  Recommended reading for those interested in this topic: Lessons from malaria control to help meet the rising challenge of dengue

# # # # #

Author’s Comment Policy:

 Please try to stay on topic — I know it is a real temptation to simply rail against models and modelling but that is not the real problem with this paper or its use as climate change propaganda by the NY Times.

I think that there has been a failure to review the results of their models against biological and sociological/political plausibility.

I’d like to read your views on the subject. Address your comment to “Kip…” if you are ‘speaking’ to me.

# # # # #


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June 11, 2019 10:08 am

As I understand it genetic engineering has the tools to eradicate this mosquito

June 11, 2019 11:04 am

MIKE MCHENRY ==> There are some genetic engineering solutions to mosquito populations such as the introduction of thousands of sterile males. In the US, there has been a lot of push back against using the technology despite its apparent advantages — NIMBY knee jerk reactions to the words “genetic engineering”.

Clyde Spencer
Reply to  Kip Hansen
June 11, 2019 1:42 pm

When I was in the Army, the captain at the lab (the only one!), Dr. Knipling, was the son of the man who executed the plan to eradicate the screw worm that was infecting cattle in Texas and other southern states. It wasn’t genetic engineering, they just exposed the male screw worms to a gamma ray dose high enough to sterilize them but not kill them. They were then released into the environment in large enough numbers to out-compete the native male screw worms. It worked very well.

Reply to  Clyde Spencer
June 11, 2019 3:23 pm

I can hear the know nothings ranting against radioactive mosquitos.

Clyde Spencer
Reply to  MarkW
June 11, 2019 8:47 pm

It would be very helpful to people if mosquitoes glowed in the dark! 🙂

June 11, 2019 11:30 am

However, by eliminating the mosquito, you put at risk the food source for many species including birds, bats, reptiles and fish. Better to eliminate the cause of the disease rather than the vector.

Reply to  Greytide
June 11, 2019 12:34 pm

Greytide ==> The advantage of the SIT (Sterile Insect Technique) is that it fgocuses on specific insect or mosquito breeds….there are plenty of others to feed the insects. Eliminating Ae. Aegytpti or greating reducing their prevalence in a slum could save thousands of human lives. It is not the same as wholesale insect elimination using broad-effect insecticides.

Reply to  Kip Hansen
June 11, 2019 1:32 pm

Kip…… I take your point but, even so, tackling the actual cause of the disease rather than the vector should be the way to go. STI is only addressing the route of transmission. This can also be addressed by DDT or reducing breeding sites near populations as you mention above. These have the advantage of not disrupting the mosquito population too much. Man has not got a good record of intervention in biological control (Cane toads etc) as we rarely seem to look at (or maybe understand) the bigger picture. Maybe all we would do is push the microbes to a different vector?

Reply to  Greytide
June 11, 2019 12:50 pm

Kip, at this point Florida is trying several sterile male experiments attempting to control Aedes aegypti. Two use some form of radiation and two use bacteria. Indeed the push back from environmental groups has been and will remain intense. Their reasoning is profoundly bizarre. However after the Zika outbreak in Dade County our state government is presently moving forward. It was more difficult when Obama-Biden were in charge.

Note: Zika, Dengue, Yellow Fever, West Nile, St. Louis Encephalitis, etc all are Flaviviruses. A couple require a primary host, usually a bird. Yet the scary thing for those that are human-mosquito-human transmission is that some people can be viremic yet be asymptomatic. It is how Zika got here from Brazil.

You didn’t mention Aedes albopictus, the Asian Tiger Mosquito. It has the same breeding habits as A. aegypti and can actually displace aegypti. Even though they arrived in the US SE Tigers are far more cold tolerant and are considered viable vectors. They are also daytime aggressive biters. Tigers arrived due to Jimmy Carter energy policies. We were importing used tires to burn as fuel.

The last significant malaria epidemic took place in Perry, Florida SE of Tallahassee in 1949. It was controlled primarily, though not exclusively, by putting screens on everybody’s windows and the careful use of DDT.

Probably the single biggest reason we are seeing arthrovectored diseases on the rise is modern air travel and improving economics that allow people to travel, for example, from Africa to Brazil for the World Cup Soccer and the Olympics.

One final note, ‘experts’ believed in your bottomline number one. In Puerto Rico dengue is endemic with the occasional epidemic breaking out. It was assumed the epidemics originated in lower class neighborhoods. They did a mark capture program and tracked much of the breeding and dengue virus to a middle and upper middle class neighborhoods. People were not doing good “sanitation.” They were breeding mosquitoes in fountains, kids toys, swimming pools, rain gutters, etc.

Aedes aegypti is difficult to control using standard spray techniques, e.g., truck spraying and even aerial spraying. While backpack sprayers are an adequate tool and can help knock back the population, the problem is pesticide resistance and pushback from environmentalists. It is always better to stopping breeding by treating or better eliminating breeding sites. Most aegypti are “homegrown.” People do not like to hear that having dealt with the issue in public hearings.

Dr Deanster
Reply to  Edwin
June 11, 2019 1:40 pm

Yep …. “this is how Zika got here from Brazil” ….. this very real fact is a major issue about letting tens of thousands of illegal immigrants just Willy Nilly cross our southern border. They bring South American diseases that are not normal for this area.

Of course, in the typical leftist perspective, they will just chalk it up as “social justice” for Europeans bringing small pox here 100s of years ago.

Paul Milenkovic
Reply to  Edwin
June 11, 2019 2:16 pm

I kind of wonder why malaria has not made a comeback in the US in places where there were malaria cases in the past? This is especially since the powers-that-be have pretty much given up on spraying against mosquitoes.

On possible explanation is air conditioning and window screens. We pretty much keep mosquitoes out of our homes, so if there is a malaria/dengue case, that person doesn’t get bitten and then spread it to other people? I guess with West Nile there is a reservoir of bird infections and with Zika, as you mentioned, asymptomatic persons as carriers.

As to spraying, what is the go-to agent these days?

As to habitat, with the West Nile concern here in Wisconsin, people are pretty careless and care-free about standing water. I am a contributor because my property has tall trees, my gutters fill up with leaves and sticks, and there is standing water until I get up on a ladder to drain them. Anyone here know a good type of gutter cover to install?

Joel O’Bryan
Reply to  Paul Milenkovic
June 11, 2019 4:09 pm

The Malaria vector is the Anopheles mosquito. It has a very different ecology from Aedes. Making it easier to control in cooler climates and with insecticides. Anopheles is primarily a night feeder, where DDT treated mosquito nets over sleeping beds can be quite effective.

Reply to  Joel O’Bryan
June 11, 2019 6:14 pm

Anopheles is primarily a night feeder, where DDT treated mosquito nets over sleeping beds can be quite effective.

Often claimed by people who want to kill innocents by disease (er, oppose DDT use properly), but not true in most cases. (Yes, in the classroom abstract. In the real world of dusk-to-dawn life, when mosquitoes begin feeding before dusk and stop well after dawn? People cannot crouch under special blankets all night long!)

Reply to  Paul Milenkovic
June 13, 2019 11:25 am

Joel O’Bryan is right. Malaria is mostly transmitted indoors and at night. That is why even untreated mosquito netting is useful (though less reliable than DDT).

In northern Europe where malaria was common up to c. 1850 it was even mostly transmitted by overwintering Anopheles indoors, and most cases therefore occurred in spring, before the “mosquito season”. It disappeared with better housing, though there is still plenty of Anopheles around.

Reply to  Paul Milenkovic
June 15, 2019 3:58 am

The ‘Anopheles’ mosquito is actually many different species of mosquitoes with many different habitat, biting time, and host preferences. Last I read, all that had been tested in the lab could transmit malaria, but in reality most don’t. Most of the most efficient vectors are night-time biters in many parts of the world, but others are late afternoon or crepuscular biters. So, you really need to know your local epidemiology before relaying on bed-netting and the best practice is to try to avoid being bitten and take your pills.

Malaria has been making very localised ‘comebacks’ in Western countries (‘airport malaria’ etc.), but outbreaks have been small. An epidemic would require a large reservoir of infected people to infect the mosquitoes and a totally nonfunctional public health system. So far this has not happened, but I would not be excessively complacent.

Reply to  Edwin
June 12, 2019 9:50 am

Edwin ==> Yes, lived in Florida some winters recently and was aware of the controversy over genetically modified (sterile) mosquitoes.

To control dengue it is necessary to do “all of the above” — like malaria or yellow fever. Spray environment (including backyards), public education on breeding sites (tires, tin cans, kids toys, water in rain barrels and gutters, etc), isolation of infected persons until they are no longer viremic. This must be kept up as a serious effort until dengue is no longer endemic.

It is much easier to keep dengue from getting established than it is to get rid of it after the fact.

Reply to  Edwin
June 15, 2019 4:44 am

Hi Edwin – thanks for the informative comment. I would just note that the Caribbean Treehole Mosquito Aedes mediovittatus is a complicating factor in Puerto Rico and the rest of the Caribbean as it doesn’t mind feeding on people and is a competent dengue vector in the lab. Also, we were able to control Aedes aegypti well before the advent of synthetic pesticides and I don’t see much use in the sterile male or Wolbachia techniques except as very expensive adjuncts to sanitation, interesting science though they may be. As you note, controlling breeding is the key and was demonstrated as effective more than a century ago. Can’t really see any local governments actually getting this accomplished now though, not even if a new Fred Soper should emerge. Too much fear and misinformation around and a MSM that thrives on it.

Reply to  Greytide
June 11, 2019 1:05 pm

Isn’t covering water barrels, dumping water, etc an attempt to destroy the mosquito population? Unless there is a magical, miracle cure for the fever, the mosquitoes die or the disease spreads.

Reply to  Sheri
June 14, 2019 9:17 am

Sheri ==> That is not the case. The map of the United States (blue map) from the CDC shows that the main insect vector for dengue already lives and breeds freely in much of the United States, yet dengue is almost entirely unknown here. Transmission of dengue requires humans infected with dengue as a prerequisite — the mosquitoes MUST bite an infected human to become infected themselves, before they can transmit dengue to another uninfected human. Without infected humans available to be bitten, there is no dengue to spread.

Reply to  Greytide
June 11, 2019 1:29 pm

Aedes aegypti is pretty much concentrated in towns and cities. And even if it was eliminated there wouldn’t be a mosquito shortage, there are plenty of other species.

Reply to  Greytide
June 11, 2019 6:33 pm

Greytide – you are completely off mark here. Aedes aegypti and albopictus are weeds. They only live around people and are not part of any natural food webs. Completely eliminating them would have zero effect on any bird and bats, except probably to make their lives less itchy. There are no fish in the small accumulations of water these mosquitoes breed in. It’s possible that synanthropic geckoes and other small lizards that live with people might miss a meal or two, but mosquitoes are pretty small prey and there is no data showing that any vertebrates need these mosquitoes to survive. Even house spiders rarely catch mosquitoes. Without these mosquitoes there would be no dengue, zika, etc. and only Yellow Fever in jungle areas with native mosquito vectors.

Reply to  DaveW
June 13, 2019 8:27 am

DaveW….. I think you really make my point. You call Aedes a “weed”. Weeds are generally plants where we don’t want them but, we have found that when we remove them, we can have a profound effect on food chains. They are essential in so many food chains. They now pay farmers to grow “Weeds”. I very much doubt that “Weeds” (Aedes) evolved around humans and are just using our environment as an easy way of life. We may think we know a lot but really we know next to nothing and we interfere at our peril.

Reply to  Greytide
June 15, 2019 3:33 am

Greytide – I don’t know where you get your information, but I use ‘weed’ in the usual sense – an introduced species that thrives in disturbed habitats (aka an ‘invasive species’). Rats are weeds in this sense as are the Aedes (Stegomyia) species that live around people and feed on us preferentially. It is true that ‘weeds’ are sometimes native species that like the way we disturb ecosystems, but mostly they are hitchhikers from other parts of the world that breed fast and have little or no natural controls. I don’t know of anyone who is getting paid to grow weeds, although I understand growing weed can be profitable and is now legal in parts of the US.

Aedes is a genus, not a species – there are many hundreds of Aedes species many of which are ‘natural’, some annoying, some are disease vectors to us and to other mammals and birds but don’t produce epidemics, and others of little to no public health interest. The subgenus Stegomyia includes two invasive species that both prefer to breed around and feed on people (and also dogs, but much less so on other synanthropic vertebrates) and transmit a host of nasty arboviruses. These are invasive species and have no relationship to ecosystems outside of areas of high human impact. I think we know a lot about these particular mosquito species and we have had the knowledge to control them for well over a century, but we just do not have the political will. So if some day you or someone you know has the misfortune to contract one of these diseases, I hope you have access to good medical care and a GP who knows something about arboviruses and doesn’t think they are just a problem in a 3rd world tropical country.

Walter Sobchak
Reply to  Greytide
June 12, 2019 8:48 am

So we need to eliminate mosquitoes and environmentalists. Equally annoying and equally useless.

Charles Higley
Reply to  Greytide
June 12, 2019 11:51 am

I t could be argued that eliminating the mosquito would not seriously disrupt the food web as there are so many other insects that these organisms also eat. The benefits of such an elimination and the resulting adjustments of the food web vastly outweigh the negatives. We should encourage mosquitoes? Not going to happen.

June 11, 2019 10:16 am

Kip: Thank you for providing an true epidemiological view of the risks of vector born diseases. People in the developed west have plenty of other disease entities to worry about without fretting over these.

Reply to  Scott
June 11, 2019 12:37 pm

Scott ==> Yes, my objections are heuse of this study — in the public media — to scare people about innocuous warming. The MAP of increased risk, used in the NY Times is simply not biologically or sociologically/politically plausible.

Reply to  Kip Hansen
June 11, 2019 4:50 pm

…the use of this …

steven mosher
Reply to  Kip Hansen
June 12, 2019 12:48 am

then you should have given a fair assesment of the study and focused your attack on the misuse


mark from the midwest
Reply to  Scott
June 11, 2019 1:01 pm

Like heart disease

Reply to  Scott
June 11, 2019 1:48 pm

And most of the ones we get, we didn’t see coming. West Nile, anyone? Measles resurgence? Anything COULD happen–asteroids, hemmorhoids . . . it seems 2/3 of the “news” lately is speculative “scare” articles; anything from stock market crashes to Climate everything COULD happen, but so could winning the lottery. Does that keep us up at night? 😉

Mark Broderick
June 11, 2019 10:20 am

” Thus, teo (two)? things are necessary for the occurrence of dengue fever in a human population: ”

Kip Hansen

Reply to  Mark Broderick
June 11, 2019 11:09 am

Mark ==> Thanks for reading closely — WordPress has been slow with updating my corrections. There are a couple more typos ….

June 11, 2019 10:25 am

These days, there is no known horrible disease, awful climate disaster, social problem, or ethical dilemma which will not be made a thousand times worse very very soon, at least, in the minds of all Global Warmers, The NY Times, the Grauniad and their fellow travellers.

Mark Broderick
June 11, 2019 10:27 am

Kip correction…

“Backpack sprayers, which look oddly like those featured in Ghost Busters, (a)re very effective in knocking down mosquito populations in crowded cities with their narrow alleyways between and behind houses.”

great post again…

Mark Broderick
June 11, 2019 10:33 am


“As for Africa, India, China, and SE Asia, as population increases and concentrates in cities, the poor will live in slums, riff (ripe?) for dengue,”

Reply to  Mark Broderick
June 11, 2019 11:11 am

Mark ==> I think you’ve found them all now …. hopefully, Word Press will push out the updates and the typos will disappear from the visible essay.

June 11, 2019 10:37 am

…dengue needs people with it first

The last outbreak in Florida was illegals/migrants working the fields around the lake…it was in the news…then disappeared

The outbreak in Key West….about 5% of the people tested…tested positive to the antibodies

Reply to  Latitude
June 11, 2019 11:15 am

Latitude ==> Yes, occurrences of dengue in the US depend on humans bringing the virus into the US inside their bodies (infected people coming to or returning to the US). The mosquitoes necessary already exist and live and breed here. Florida and the Keys have a few cases each year as a result. But the disease does not establish itself here as the US lacks the two main ingredients for endemic dengue — crowded slum conditions and high populations of tboth the mosquito and infected humans.

Reply to  Kip Hansen
June 11, 2019 12:47 pm

well all that…..and we declare all out chemical warfare


…and everyone’s new favorite….Naled

Clyde Spencer
Reply to  Kip Hansen
June 11, 2019 1:59 pm

You said, “… the US lacks the two main ingredients for endemic dengue — crowded slum conditions and high populations of tboth the mosquito and infected humans.” I think it is also very important that there are few US dwellings without window screens.

I have a friend teaching in Africa and he told me that window screens are virtually unknown, even in high-class hotels and the universities. He is currently in Ethiopia and was previously in Tanzania.

I once had the good fortune to meet a descendant of the 49ers in California. He inherited a large ranch near the Merced River. His great-grandparents(?) realized that there was malaria in the state, so they built their two-story family house more than a mile from the river to stay away from the mosquitoes. It gets pretty hot and dry in the Summer when one gets away from water, so the mosquitoes were not a problem.

Reply to  Clyde Spencer
June 11, 2019 4:49 pm

Edwin ==> There is a huge difference between Anthroponoses and Zoonoses. A quick primer can be the abstract of this paper from the CDC.

“zoonoses” are “diseases and infections which are naturally transmitted between vertebrate animals and man”

Anthroponoses (Greek “anthrópos” = man, “nosos” = disease) are diseases transmissible from human to human.

It gets complicated, but dengue is transmitted from infected human to uninfected humans by the Ae. aegypti mosquito. There is no other host animal involved — other than the insect vector — without sick humans, dengue goes away.

The spraying I mention in the Dominican Republic could never have been carried out inthe United States — you have that right.. Even I was somewhat appalled as the clouds of “human’safe” insecticide rolled down the streets while the residents laughed and danced in the clouds.

Reply to  Clyde Spencer
June 11, 2019 4:53 pm

Clyde ==> Poverty means exposure to illnesses like dengue — it takes money to have windows (with glass) and window screes, and screen doors. Having adequate food usually comes first.

Clyde Spencer
Reply to  Kip Hansen
June 11, 2019 8:52 pm

I’m well aware of the problems of poverty. The point I was trying to make is that it is unlikely that the US has high risk of becoming a reservoir for dengue or malaria precisely because so many people are protected from being bitten while sleeping, and therefore few mosquitoes will get infected and be able to pass the virus on to others.

Reply to  Kip Hansen
June 12, 2019 6:33 am

Clyde ==> Yes, you are exactly right about that.

Reply to  Kip Hansen
June 15, 2019 5:06 am

Clyde et al – screens, ariconditioning, etc. are great, but Aedes aegypti will bite you any time of the day and anywhere it can find you. To quote WHO (Stegomyia is the subgenus including both aegypti and albopictus):

“Dengue infection rates are higher outdoors and during daytime, when these mosquitoes (Stegomyia) bite most frequently. However, Ae. aegypti breed indoors and are capable of biting anyone throughout the day. The indoor habitat is less susceptible to climatic variations and increases the mosquitoes’ longevity.”

My guess is that it is the lack of a large enough reservoir of infected (including viremic, but not symptomatic) people in areas with well established populations of Aedes aegypti that has so far protected the US (and Australia where I reside and worry – A. aegypti is only an hour’s drive north of where I live and there are yearly outbreaks of dengue – typically an entire street at a time – farther north) from more local outbreaks of the host of nasty arbovirus-caused diseases vectored by these mosquitoes. Really, governments and people are far too complacent about ‘tropical diseases’. Look at the outbreaks of Murine Typhus in LA.

June 11, 2019 10:39 am

The focus on temperature as the primary disease vector is of course convenient to the climate alarmist viewpoint, but as you say, Kip, history tells us otherwise. Mosquitoes breed everywhere there is sufficient moisture – some of the buggiest places on earth, with humongous mosquito populations, are in the great northern boreal forests of North America and Siberia.

History also teaches us that most of the worst disease pandemics occurred during cold periods – primarily because human populations are substantially weakend by malnutrition, which is of course a direct result of crop failures due to cold climate eras. The Justinian Plague in the middle of the first millenium … the Black Death plague in Europe in the 14th century, and the last great outbreak of bubonic plague in the late 19th century – every single one of these mass pandemics occurred during cold eras characterized by mass crop failures and starvation, along with increased human comunnication due to trade and empire, and of course total lack of modern sanitation and housing and medicines and such.

The point is that the full risk profile of a disease comes into play – a course virus or bacterium … a vector capable of transmitting the disease … and a susceptible human population are ALL required to create a disease pandemic.

Reply to  Duane
June 11, 2019 11:18 am

Duane ==> Quite right — the Ae. Aegytpti mosquito however can not live in very cold areas (or very dry areas). But we already have the mosquitoes in much of the United States and for the reasons you point out, we don’t have endemic or epidemic dengue — nor do we have yellow fever.

Reply to  Kip Hansen
June 12, 2019 6:09 am

Kip – also, that a particular mosquito such as Ae. Aegytpi is associated with a particular disease does not mean that other mosquito species cannot transmit the virus or bacterium. It just means that those other mosquitoes that may live in other parts of the world – such as the near arctic boreal forests – simply have not had the opportunity to serve as a disease vector. After all, the human population density in the high north is extremely low as compared to the human population density in much of the humid tropical regions, so there is literally no opportunity for the mosquitoes in the high north to make contact with the dengue fever virus.

Ae. Aegytpi was also identified as the principal carrier of the Zika virus a few years ago when Zika fever became a big panic here in Florida where I live. These mosquitoes have thrived here forever, along with many dozens of other mosquito species here in the swamps of South Florida. The media and CDC and state and local health authorities managed to create a massive panic over Zika, spraying the hell out of everything here in South Florida, scaring the tourists, etc. etc. etc. But it turned out that virtually 100% of the identified cases of Zika contracted the virus in South America or Central America – where all of the other predicates for virus transmission exist, but not here in South Florida.

Like the old saying goes, “it takes two to tango”, it takes a virus, a vector, and a susceptible human population to make an epidemic or pandemic.

steven mosher
Reply to  Duane
June 12, 2019 12:51 am

except they looked at temperature, precipitation, population

they made circumspect claims.

the media misused it

Reply to  steven mosher
June 12, 2019 6:38 am

NMosher ==> You have to actually read all the materials — not just the bits you want if you’re going to discuss essays here. The NY Times did its [nutty at this stage in the climate game] due diligence by interviewing a major co-author, Oliver J. Brady, and included his promulgation of “increased risk of dengue” in the United States and re-stating that controlling CO2 emissions might help stop the spread of dengue. Both idiotic ideas.

June 11, 2019 10:45 am

Well done Kip.

Sadly you’ve used facts and information, the world has little use for that.

Many of the issues with regards to Dengue are similar to Malaria as you pointed out. Always a handy read:

The author, Paul Reiter, is now vilified by the climate community at large, including some entomologists, as a “denier” because of that paper. That notion is patently absurd.

It’s quite disturbing how much money will alter people’s opinions, especially grant money. When I first joined the entomological Society of America there were no climate change related talks at the annual meeting. I’d guestimate that perhaps 20-30% or more are aligned with the topic now. There is an awful lot of money to be had for work. I understand the obtaining of the money to put grad students through and maintain programs. What I don’t understand is the lack of objectivity in reporting the results.

Reply to  buggs
June 11, 2019 12:40 pm

buggs == Thanks for the Reiter link. Therre is a great deal of silliness going on about slight general warming and tropical diseases (which are called tropical today, but historically not confined to the tropics.)

Reply to  Kip Hansen
June 11, 2019 1:28 pm

Indeed the very name Malaria stems from Venice in the northern Adriatic. So named due to the stench exuding from the nearby swampy shores. ‘Mal aria’ literally means ‘bad air’.
It only is endemic to areas where lax sanitation is prevalent and people live cheek to jowl.

Reply to  Rocketscientist
June 11, 2019 7:41 pm

Leningrad (St Petersburg at the time), upstate NY while digging the Eire Canal, England, Canada, midwest … All had outbreaks far north of 40 deg latitude.

Reply to  RACookPE1978
June 12, 2019 1:46 am

Northern Russian cities, such as St. Petersburg, Novgorod, etc., are notorious for swarms of mosquitoes breeding in plumbing and drainage systems. It’s the worst at night but these bloodsuckers are present in the daytime, too — and no window screens help, because they actually live within the multi-apartment houses, hiding in poorly fitted, almost never disinfected pipeworks.

Not to mention mountains (literally) of wet garbage filling interior courts, dead-water puddles everywhere, multiple canals and backwaters. It doesn’t matter if your bedroom is on the third or sixth floor — they are flying in from the cracks in the walls, they smell you, they find you, they bite, they don’t let you sleep, and their bites itch like hell.

I believe there is already a subspecies of northern Russian “house mosquitoes” — smallish, pale, almost white, difficult to see against the background of ceilings and walls, silently flying… a plague of life in summer.

Alan the Brit
Reply to  buggs
June 11, 2019 1:17 pm

I’ve read a coule of papers by Prof(Dr?) Reiter, they are very informative & written in such a way as to be generally understood by the lay (non-scientific) person. I am an engineer so can follow the general discourse!

AsI have said here before, (via Prof Reiter), the Ague is mentioned in the works of Shakespeare over a dozen times, an era not noted for its tropical warmth!!! Malaria comes from the Italian for bad air, when they thought it was an airborne disease, which via its carrier makes it so!

Steven Mosher
June 11, 2019 10:55 am


what they are predicting is ‘ dengue suitability ” to the extent that this is conditioned by their selected variables. The key word is SUITABILITY. Note they are not predicting occurance

to your points

“1. Dengue is a mosquito borne disease that depends on poor sanitation and non-existent vector control to remain a problem in areas where it is endemic. It can be eliminated, just like yellow fever and malaria were eliminated in the United States.”

This says nothing about their map of SUITABILITY. Of course it can be eliminated. That is not the point
in a risk assessment. Suppose the fire marshal came to your property and pointed out that all the underbrush beneath your trees increased your fire risk and your said “well any fire could be put out!”

” 2. Raising standards of living high enough to allow homes to be protected with screened windows, screen doors, municipal water (with pipes) and to have reliable functioning trash collection will eliminate much of the dengue load in a country.”

Yup. the fire can be put out. Might want to prevent a fire rather than put one out, but yes, fires can be put out,

“3. Public health programs that inform the population of risks and instruct them to eliminate breeding spots for mosquitoes, along with serious vector control (spraying) reduces risk.”

Yup, noting that risk can be reduced is besides the point of their suitability projections

4. Where dengue is endemic and epidemic, it is a real ongoing public health problem and should not be ignored or brushed off, even if this new paper exaggerates the increasing risks — in some countries it is just a fact of life taking children and the elderly to their graves.

err ya, beside the point

“5. It is unreasonable to maintain that as these developing countries advance that they will not achieve the two items (2 and 3) above….international aid programs can help in this regard and will do much more to protect the health of people than any of the climate change initiatives being pushed by political activists.”

again unrelated to their claim

Now, where you do look at their claims

“The Messina et al. projections of dengue risk in the American south and in the desert areas of southern Arizona and New Mexico are not biologically plausible when one takes into account current living standards and modern vector control efforts already extant in these areas.”

A couple points. you left off charts d,e and f which showed expansion, contraction and stability.
You should probably look closer at the maps.. what exactly are the the claims the make for Arizona and New mexico?

did they make any claims?

here is what they claimed

” Overall, we predict
minimal changes in the total global area at risk of dengue, but significant subnational changes in risk distributions between 2015 and
2080 (Fig. 2). Much of the southeastern USA is predicted to become
suitable by 2050″

and arizona is where?


” At the same time, there
are a number of areas where we predict contraction of dengue suitability. Some areas in central East Africa are predicted to see declining suitability as they become hotter and drier”

So what is the point of these types of forecasts

“Any long-term future projection is subject to a range of assumptions and limitations. In particular, we assume the stationarity of the
effects and interactions of drivers of dengue transmission, and the
absence of innovations and improvements in dengue control. There
is also considerable uncertainty in the structure of the models used
to predict future climate, Aedes distribution and dengue risk, which
we have endeavoured to appropriately quantify and propagate by
using ensembles of 17 different climate models and 100 dengue risk
models. Despite these limitations, projections using the best possible compendium of dengue occurrence currently available have
considerable public health value because detailed, systematically
derived projections provide an evidence base that can be updated
through time for prioritizing resources and informing long-term
planning. ”

Now as you note some things where left out of the modelling

this ISNT news to the authors

” Future
work should include intervention scenarios based on current
(insecticide and source reduction) and emerging (vaccine, sterile
insect technique and Wolbachia) tools. ”


” We have provided a set of maps
(with appropriate caveats) identifying three possible futures for the
global distribution of dengue until the year 2080. We have incorporated information about the spread of Aedes vectors, urbanization
and population growth, showing that while climate change will be
important, so will other drivers of disease distribution and abundance. Although there will be increases and decreases, we expect
that the populations at greatest risk of this disease will grow substantially and disproportionately in the most economically disadvantaged areas”

Reply to  Steven Mosher
June 11, 2019 11:08 am

Mosher ==> Thanks for weighing in and defending what was not under attack — but nice to hear from you.

steven mosher
Reply to  Kip Hansen
June 12, 2019 12:54 am

kip. precisely. you didnt touch the paper.
still curious about your claim about the maps of arizona and new mexico, and why you failed to show d,e and f

Reply to  steven mosher
June 12, 2019 3:35 am


Reply to  steven mosher
June 12, 2019 6:30 am

Mosher ==> This essay isn’t an attack on the paper, other than the author’s apparently lack of applying a little bit of reality checking their model results, thus predicting not only “Globally we predict 2.25 (1.27–2.80) billion more people will be at risk of dengue in 2080 compared to 2015, bringing the total population at risk to over 6.1 (4.7–6.9) billion (Table 2), or 60% of the world’s population, according to RCP6.0/SSP2..” (that is a direct quote from the paper). Their map, as recolored by the NY Times (the brown map in the essay), shows higher dengue risk throughout the American Southern States, including all of Florida, creeping up from Mexico into southern Arizona and New Mexico (areas which are desert in long-term drought) — it does not show just “environmental suitability”.

I would never even bother to attack a paper that depended on so many arbitrary selections of results from among so many [chaotic] model outputs….that would be a waste of time.

The CDC map showing current existing Ae Aegypti range clearly shows that they did not reality check the prediction, at least the US parts, as 2017 Ae Aegypti range is much larger than their predicted range of “increased risk”…, if the map is not expansion of Ae Aegyo=pti range, then did they think these areas of the US would develop third world slums? or that housing standards would fall so far as to omit window and doorway screens? Maybe their model predicts that Florida will curtail all vector control? see…. just not plausible…..

Of course the NY Times misused the study — that is a given. But one of the co-authors is quoted specifically in the Times predicting increasing risk of dengue in the United States. and the same co-author, “Dr. Brady said, ‘hints at the idea that if we do control emissions better, we could stop or at least limit this kind of spread.’”.

So, can’t all be blamed on the Times…..

John Mclondon
Reply to  Kip Hansen
June 14, 2019 1:55 pm

“The mosquito that transmits dengue fever is found in Texas and across the southeastern U.S., so there is a potential risk for dengue transmission. Sporadic outbreaks have occurred in the Gulf coastal area and in extreme south Texas.” according to the Texas Department of Health Services. Even in the tropical regions in India, most of the transmission does not occur within the house (they usually run fans within the house) but outside. So window screens do not play a major role, I think.

John Mclondon
Reply to  Kip Hansen
June 14, 2019 1:57 pm

ps. also it seems DEET is losing its effect

Reply to  Kip Hansen
June 14, 2019 7:36 pm

John ==> Yes, Ae. aegypti thrives in Texas (see the blue US map in the essay). But for dengue to exist, there must be humans viremic (infected with the dengue virus) for the mosquitoes to get the virus from before they can infect other humans. This does occasionally happen when an infected person enters the United States — then, depending on where and when and conditions where the infected person resides, there can be a few cases develop. Quarantining the infected persons (usually, just hospitalization) stops the spread and the little local “epidemic” ends.

This most often happens in communities with ties to the Caribbean and parts of Mexico (where dengue is endemic).

Reply to  Steven Mosher
June 11, 2019 12:22 pm

“Suppose the fire marshal came to your property and pointed out that all the underbrush beneath your trees increased your fire risk ….”

Suppose a different fire marshal ignored the brush beneath your trees and pointed out that your home is combustible … and recommended that you have it (the home) removed so as to better protect yourself from a brush fire (and to protect the brush from your inevitable home fire).

Then suppose how you would respond to the fire marshal.

Then suppose how you would react to the fire marshal telling you that your denial of the potential harm your home my cause to the brush (and other peoples brush) is selfish and stupid.


Robert Balic
Reply to  DonM
June 11, 2019 7:16 pm

Suppose they told you that you couldn’t protect your home except by reducing your carbon footprint.

“They were labelled law breakers, fined $50,000 and left emotionally and financially drained.

But seven years after the Sheahans bulldozed trees to make a fire break — an act that got them dragged before a magistrate and penalised — they feel vindicated. Their house is one of the few in Reedy Creek, Victoria, still standing”

Reply to  DonM
June 11, 2019 7:50 pm

And three enviro groups sue you because you DID TRY to cut down the brush and bushes around your house?

John in Oz
Reply to  Steven Mosher
June 11, 2019 3:11 pm

the absence of innovations and improvements in dengue control.


This statement alone should make you think twice about defending this ‘study’, let alone the 100 BRT models and 17 GCMs with the assumption that averaging their output will have any validity.

You also (cynically) state for Kip’s point 2 that

” 2. Raising standards of living high enough to allow homes to be protected with screened windows, screen doors, municipal water (with pipes) and to have reliable functioning trash collection will eliminate much of the dengue load in a country.”

Yup. the fire can be put out. Might want to prevent a fire rather than put one out, but yes, fires can be put out,

This point is entirely about prevention, not treatment after infection. You criticise Kip for missing the point of the study then make the same error yourself.

“And why behold you the mote that is in your brother’s eye, but consider not the beam that is in your own eye?” Luke 6:41,42

June 11, 2019 11:02 am

Readers ==> There are a couple of typos in the essay — Word Press is a little slow today in updating with my corrections.

Robin Beran
June 11, 2019 11:09 am

So basically, other than the new 3rd World locations of SF and LA, the spread into the US is pretty unlikely.

Andy Pattullo
June 11, 2019 11:37 am

Thanks, great article. I recently lectured on supposed climate change links for malaria and Lyme disease. Similar issues. Lyme disease increased in areas that have been cooling, not warming and that was largely due to land use changes: reforestation, deer population explosion and increased human contacts. At the same time malaria incidence fell in endemic areas resulting in the saving of millions of lives among the very young due to increase vector (mosquito) control once the jurisdictions involved realized they needed to return to use of DDT for local spraying. It isn’t that climate factors don’t have influence – it’s just that there are many other factors that are as or more important to arthropod-borne disease spread.

Reply to  Andy Pattullo
June 11, 2019 12:47 pm

Andy Pattullo ==> It is quite a wonder that real science journalists [mostly] do not actually do any fact checking on these issues, but simply repeat and exaggerate claims made of “2.5 billion more people will be at risk” and then show a map of dengue spreading into the southern US states, Arizona and New Mexico, and northern Australia.

Thanks for your input.

Thomas Homer
June 11, 2019 11:43 am

Yet, here in the U.S., vernal pools must be protected:

“The vernal pools serve as essential breeding habitat for certain species of wildlife, including salamanders and frogs (amphibians). Juvenile and adult amphibians associated with vernal pools provide an important food source for small carnivores as well as large game species.”

“Starting September 1, 2007, significant vernal pool habitat is protected by law under the Natural Resources Protection Act (NRPA). An activity in, on, or over these areas must avoid unreasonable impacts on the significant vernal pool habitat and obtain approval from the DEP, through a Permit by Rule or individual NRPA approval.”

Tom Halla
Reply to  Thomas Homer
June 11, 2019 12:46 pm

From what I know about A aegypti, the species rarely breeds in larger natural water bodies, usually fairly small artificial containers, like used tires or water containers.
While other species of mosquito will breed in vernal pools, apparently for A aegypti that is not a favored breeding site.

Reply to  Thomas Homer
June 11, 2019 12:49 pm

Thomas Homer ==> In some parts of the US, vector control (mosquito spraying) had been discontinued in the past — which was a mistake. even now, not all areas have taking up the campaign again.

June 11, 2019 11:55 am

I caught Dengue Fever 3-4 months ago while wintering in SE Asia. It is very bad experience, and there is no real cure, just treatment which is mainly hydration and rest. If really bad, then the only hope is being on intravenous hydration and electrolytes in a hospital. Hope for A/C. I was able to hunker down for a week to 10 days at a friends hotel resort and the time to clear is about 13-14 days, but did have to fly 3 flights back to N/A over 2 days at the end which was a very miserable and scary proposition. I was having fits of fever that would come and go, but luckily it was the tail end of that ordeal.

As the article points out, it needs a critical human population density to be infected with Dengue in order for local mosquitoes to bite and spread. I don’t think global warming has much to do with it as much of any warming is happening in the winter and at night at northerly latitudes, or is UHI. Plus I already have 100x the mosquitoes in the boreal forest/mountains as any jungle and the season isn’t going to get that much longer for mosquitoes. Dengue is prevalent in 3-4 kinds of mosquitoes and unless it jumps to new mosquito species, I don’t think it is a threat where it isn’t already a threat. There is no real protection other than prevention of mosquito breeding ground and/or mechanical protection like screens or bug dope. The locals, who many live in open bamboo thatch and open windows have no defence except maybe a mosquito net for sleeping. That doesn’t help much for the rest of the day, so then they have a coconut shell fire smouldering for smoke/smudge, which is a real awful smelling all the time. Eradicating the mosquito breeding ground is paramount, but that isn’t practical in monsoon season.

Kids die the most it seems, because the fever gets so high so quick and they die from internal bleeding. The Philippines tried the Dengue vaccine Dengvaxia on 770,000 kids and some kids died from the infection it caused, causing a scandal that is still unresolved. But knowing the Philippines, it was as much the opposition making politics with the Gov’t of the day, so hard to know the truth what goes on in the Philippines. Maybe they are hoping for a big payout from the drug company. They were having a fairly severe outbreak of Dengue this winter as was some parts of Thailand to a lesser degree.

Dengvaxia is a recombinant vaccine comprising most of the proteins from the attenuated yellow fever virus vaccine, and the envelope glycoproteins from dengue virus. I don’t know if this vaccine has been found to be completely effective, (given the issues with Dengue infection) although there is supposedly work being done on 4-5 other similar vaccines. This is the best hope for dealing with Dengue Fever. I really hope they get a vaccine that works and doesn’t cost an arm and a leg making it unavailable to locals.

Reply to  Earthling2
June 11, 2019 12:53 pm

Earthling2 ==> Thanks for the personal experience of contracting dengue. My wife and I avoided it in the DR but many of our colleagues had dengue, sometimes more than once (there are several strains).

I was aware of the vaccine scandal … and as far as I know, there is still no good vaccine for dengue.

michael hart
June 11, 2019 11:57 am

“Could Dengue Spread in a Warming World?”

Maybe. Maybe not. Maybe it would spread in a cooling world too.

How about paying the relevant medical biologists and chemists a bit more for diagnosis and treatment options, and a lot less to the Global-Warming Cassandras who make a good living out of predicting long term doom? They contribute less than nothing towards human advancement.

Reply to  michael hart
June 11, 2019 12:55 pm

michael ==> yeah — that’s how it is. It will surely spread in 3rd world big city slums…..regardless of the weather.

Ron Long
June 11, 2019 12:02 pm


jim heath
June 11, 2019 12:42 pm

If all the computer models were bus routes and none of them took you to your destination a sensible person would question the bus routes, or maybe head it up with “Once upon a time” like all fairytales.

June 11, 2019 1:03 pm

The paper states “The geographical range of dengue is expected to further expand due to ongoing global phenomena including climate change and urbanization.” It seems to me that these are two separate and independent contributing factors that should not be lumped together. “Climate change” does not cause urbanization, though urbanization will definitely cause some change in local climate — however, any increase in dengue from urbanization would probably result from the increased probability of those small pockets of water in cans, tires, etc.

The slight warming of the Earth over the last 150 years is a statistical artifact of the sampled universe any way. If the nighttime temps don’t go down as much as before, the average temperature of the increases — but the daytime temperature wasn’t any higher. If springtime temperatures come a little earlier, or fall temperatures linger a little longer, the average temperature increases — but the springs and falls weren’t any warmer.

Over the last four years, 2000 well-distributed reporting stations in the continental US show cooling trends — but 6000 other, also well-distributed, reporting stations show warming trends. Neither’s are very large — barely significant — but there they are. How can such a mix of increasing and decreasing trends that barely average out to a significant value be called “climate change”?

Reply to  James Schrumpf
June 11, 2019 4:34 pm

James ==> You are correct when you say “however, any increase in dengue from urbanization would probably result from the increased probability of those small pockets of water in cans, tires, etc.”. Urban slums are hotbeds of dengue and other diseases, and the pattern has been in Asia, SE Asia, India, Pakistan, and Malaysia that the population increases happen unproportionally in and around the big cities — in slums or low-income areas.

Projected population increase probably accounts for most the projected “increased risk”.

Reply to  James Schrumpf
June 11, 2019 4:58 pm

James ==> ” any increase in dengue from urbanization would probably result from the increased probability of those small pockets of water in cans, tires, etc.” Dengue will surely increase in the crowded slums of India/Pakistan,Southeast Asia, Malaysia, and China due to the increasing numbers living in crowded slums. Nothing to do with the weather.

HD Hoese
June 11, 2019 1:04 pm

There seem to be three principal hypotheticals necessary here with caveats noted.
(1) Climate will change in the IPCC direction (“As such, in the present study we chose to present possible dengue futures based on RCPs 4.5, 6.0 and 8.5 only.”)
(2) Population (urban density) will increase
(3) Socioeconomic conditions as stated–“Shared socioeconomic pathways (SSPs) were defined previously as reference pathways that describe plausible alternate trends in the evolution of society and ecosystems over a century timescale in the absence of climate change or climate policies. ” WOW!

According to the NYT article citing the second author there is a partial solution having nothing to do with the paper. ‘The research, Dr. Brady said, “hints at the idea that if we do control emissions better, we could stop or at least limit this kind of spread.”’ Of course, this is only one of 20 authors.

Having spent a long time working around coastal mosquitoes in the future US area in question I have to ask what is the previous success predicting mosquito populations?

Reply to  HD Hoese
June 11, 2019 5:04 pm

HD ==> You missed that all the model bits were “from a choice of 100 BRT models fitted to 2015 data).” or “from a choice of 100 model predictions).” or from a choice of 17 GCMs)….on to “These 100 predictions were then summarized by mean and 95% credible intervals to give the final prediction for each year RCP combination.”

They picked and chose chaotic model results and then “found the means” of chaotic output. see Lorenz Validated.

June 11, 2019 1:21 pm

Global warming only makes cuddly animals go extinct. Mosquitoes are not cuddly.


/sarc off

Joel O’Bryan
June 11, 2019 1:36 pm

Dengue Fever Virus (DENV) is from the Flavivirus family and four common serotypes DenV 1-4. Immunity from one, does not confer antibody immunity from another serotype. So a person can get DenV 4 times as a primary infection in their lifetime.

The bad infections, the DSS/DHF syndromes, almost always come from a subsequent infection with a different serotype. This is thought (and backed up by substantial evidence) to be a result of incomplete (non-neutralizing) antibody protection to a differing serotype. This non-neutralizing antibody dependent effect (ADE) actually allows for greater cellular attachment and infection by hist immune cells for viral replication.

So your first DENV infection is almost always like a bad cold and fever, sucks but not lifethreatening. It is then a second infection, usually some years later, with a different serotype that brings about (2% or less) the bone-break fever symptoms (DHF) and dengue shock syndrome (DSS) due to plasma leakage from the capillaries under the skin.

Public health officials in the endemic areas actively monitor which serotype(s) are circulating in locales and regions. Armed with this info and the history of DENV serotype circulations, epidemologists can predict and help direct mosquito control and health resources to the areas most at risk. The WHO has been actively working this for decades and saved countless lives.

Zika Virus (ZikV) is also a flavivirus that is now sweeping through these areas, also carried by Aedes mosquitos. A pregnant woman in 1st trimester getting ZikV infection will almost certainly give birth to a baby (if born at all) with severe neural cognitive impairments, such as microencephaly, an underdeveloped brain). So ZikV is actually now a much more helath threat concern.

Fighting these viruses is what economic wealth can provide. But Energy poverty ensures vulnerable children and elderly adults continue to sleep in open huts at night during the rainy seasons when these mosquito-boorne viruses (arboviruses) are most prevalent.

Climate change policy is a far bigger threat to humanity than climate change.

Reply to  Joel O’Bryan
June 11, 2019 5:17 pm

Joel ==> you are right, improving economic conditions, both individual and national, leads to a lot of reduction in these diseases.

June 11, 2019 1:36 pm

I visited Cuba back in the early nineties, when there was officially no dengue there, but was told by the locals that there was a bad epidemic going on that the authorities were doing their best to keep under wraps. According to the Cubans the disease had come to the island with returning troops that had been fighting in Angola and Ethiopia in support of the pro-Soviet regimes there.

Joel O’Bryan
Reply to  tty
June 11, 2019 3:14 pm

Sound more like Yellow Fever virus (YFV) coming from west Africa than Dengue.
YFV is far more of a health threat due to its ability to cause neurological meningitis problems (swelling in CNS).

As far as Cuba goes, welcome Socialism and official Ministry of Truth style cover-ups.

Reply to  Joel O’Bryan
June 12, 2019 2:14 am

Neither Angola nor Ethiopia are in West Africa. And Cubans can probably distinguish dengue and “Yellow Jack”. For one thing people don’t die in large numbers from dengue.

Robert B
Reply to  tty
June 11, 2019 6:10 pm

They eventually let the cat out of the bag when it became worse.

After a devastating epidemic of dengue fever swept Cuba in 1981, claiming 158 lives, the government went after the mosquito with what public health experts describe as paramilitary zeal and soon claimed victory. But now the mosquito has signaled its return with the rising toll from dengue, a severe, flulike illness that can take a potentially fatal form known as dengue hemorrhagic fever. The number of deaths during the current epidemic has been reported variously from three to 20.

International experts say they know nothing more about the epidemic than what CubaPress, an independent news agency in Havana, has disseminated over the Web and the little the Cuban government has made officially available. But Duane Gubler, director of the Centers for Disease Control and Prevention’s division of vector-borne diseases in Fort Collins, Colorado, says he and his colleagues had suspected for some time that a problem was building. As early as the winter of 1996, the Cuban government apparently contacted the international aid group Doctors Without Frontiers, asking for insecticide to kill larvae, plus backpack sprayers for killing adult mosquitoes indoors. By the spring of last year, travelers from Cuba were talking about dengue outbreaks, but until early this June there had been no official confirmation from the government

Rod Evans
June 11, 2019 1:39 pm

Well I have been looking for a positive outcome from the global cooling phase we are in and now I see the reduction of mosquitoes looks like one positive among all the negatives the ongoing cooling will bring.
Hey ho every cloud.

Reply to  Rod Evans
June 13, 2019 11:31 am

Ho ho ho.

You have obviously never visited the northern taiga and tundra in Canada or northern Eurasia. That is where you find the real mosquito plague. You southerners just think that you have mosquito problems.

June 11, 2019 2:05 pm

Blimey , pre 1930s must have been hotter than today.

“The review paper in Lancet Infectious Diseases focused on the WHO European region (which is wider than the area commonly known as Europe). They have cited historical and recent dengue outbreaks in the region and highlighted that up until the 1930s, dengue was endemic in Europe

June 11, 2019 2:11 pm

Doesnt the world need to warm first? Dr. Roy Spencer says only .32C last month. Down over .5C the last 2 years. Anyway .32 over 40 years does not sound frightening. Especially with the AMO turning to cold phase.

June 11, 2019 3:34 pm

This nonsense was anticipated and refuted by experts writing in the Medical Journal of Australia ten years ago:
As noted above, Paul Reiter has spelt it out clearly as well. The science is settled.

Reply to  MACK
June 11, 2019 5:21 pm

Mack ==> Thanks for the Australia link….a good one.

Robert B
June 11, 2019 4:51 pm

I wouldn’t rail against modelling. Its putting forward an argument quantitatively rather than qualitatively with more hand waving than logic.

I would rail against the expertise label being awarded to those with the right politics rather than ability. The raise their deductive reasoning to divine by labelling it scientific modelling. The results are parroted by media as “evidence based research” and, even though its why quantitative arguments are better, they ignored the inductive reasoning ie the models predictions suck.

June 11, 2019 5:14 pm

Dengue is endemic where I live. “Breakbone fever”. Feels like every bone in your body is broken. We have a very competent public health agency who do their best when there is an outbreak, but some of the silliness persists. People get threatened with prosecution if water collects in flower pot saucers, old tyres and the like. The risk that gets ignored is telephone cable and similar service pits that are at natural ground level (so the agency doesn’t get blamed when someone trips over on the raised edge). I used to tip kerosene into the pit in front of my place. I now use cooking oil as its a bit cheaper. Seals the water surface enough to suffocate the larvae.
As far as I am concerned, Mosh’s “dengue suitability” refers to the suitability of the problem for reviving the global warming/climate change scam now that all the other excuses have failed.

June 11, 2019 5:24 pm

In the book: Little House on the Prairie, Laura Ingallis Wilder describes “summer fever”, a disorder more likely than not, malaria. Malaria was eliminated from most of the US by draining wetlands, hence the decreasing the density of breading mosquitoes. The introduction of DDT provided the coup de grace to mosquitos population density and a whole host of mosquito borne diseases disappeared only to re-appear when foreign visitors brought their diseases with them to our shores. However, the number of people with these diseases diminished so, along with the vector population diminishing, so too, the human population infected. There is something to be said for: “draining the swamp.”

The Northern spread of mosquitos vector borne infections will occur only with the restoration of water paradises needed by the mosquito breeding population. Keep draining the swamps. Spray DDT on the walls of living quarters. Stay safe and prosper.

June 11, 2019 5:32 pm

While its a very long time ago, I can recall as a child in India in the early
1930 tees being told that the mosquito needed to fly from one bit of
vegetation to another over a short distance.

The area as far as one could see around the military base was devoid of any
green vegetation. As a result Malaria was very rare, I never suffered from it.

Many tears later in Papua New Guinea 1956 to 1973 we never had any
problems with diseases, part due to anti Malaria pills, and even TB which
was a major problem seldom affected the Europeans.

I do recall what we used to call the smoke truck frequently driving through
the area spraying DDT. Again I never got any of the tropical

Of course none of the above would please the Greens, but I wonder if they
would be happy to suffer these diseases instead.


Reply to  Michael
June 11, 2019 6:03 pm

Depends on the type of illness (yellow fever/yellow jack is spread by a different type of mosquito than malaria), and the breeding habits of the different mosquitos. Worked in the Canal Zone as well in 1908-1914, but the French earlier never applied anti-mosquito techniques at all. (Admittedly, the theory was very young when the French were digging.)

But Hey! “Established Science” held there was no such thing as a mosquito-malaria connection!)

June 11, 2019 6:54 pm

Kip, Thanks for the informative article and paying more attention to the modelling aspect than I could bring myself to. At least one commentator seems too dense to understand that without Aedes aegypti and albopictus there would be no dengue and no Zika, etc. (albopictus is generally considered a poor vector, but I wouldn’t count on that being true forever if we keep feeding it infected people), but you explained it very clearly.

Completely missing from the paper and, as far as I’ve seen, in the comments is any historical perspective. Public health efforts were able to eliminate Aedes aegypti from most of the US and places like Brazil before WWII through aggressive sanitation primarily. After WWII with the synthetic pesticide boom Aedes aegypti was eliminated – not just controlled enough to stop transmission, but wiped out – in most of the Americas. Then the US dropped the ball and decided that wiping out the last populations in the US was not worth the hassle since we had no problems with the arbovirus-caused diseases. It seems likely that Latin America was recolonised by Aedes aegypti mostly from US populations. I don’t know anything about this University of Geneva course, but this short lecture gives a concise overview of Aedes aegypti control in the Amercas;

steven mosher
Reply to  DaveW
June 12, 2019 12:45 am

Completely missing from the paper and, as far as I’ve seen, in the comments is any historical perspective. Public health efforts were able to eliminate Aedes aegypti from most of the US and places like Brazil before WWII through aggressive sanitation primarily. ”

did you read what they say the left out?

Reply to  DaveW
June 14, 2019 7:45 pm

Dave ==> Thanks…..Endemic Dengue is kind of like a fire — you need all the ingredients to have endemic dengue, just like a fire must have oxygen, heat, and fuel, endemic dengue must have lots of breeding sites close together (the mosquitoes are limited to about a 100 yard/meter flying radius), inside that radius there must be infected humans unprotected by window screens and indoor insecticidal treatment, and uninfected humans . Getting rid of any one of these requirements eliminates dengue. Attacking all three aspects simultaneously is most effective.

Once there are no (or almost no) infected humans, dengue is no longer endemic.

June 11, 2019 11:52 pm

Speaking from personal experience, I have had Dengue and it is not pleasant! I was working in Jakarta at the time and after rainy season had passed, there was a lot of stagnant water lying around in the area next to our house. This is an ideal breeding ground, caused by poor drainage of the building site next door. The Bloody Mozzies that carry dengue are active during the day and are easy to recognize as they are prominently marked by stripes on their legs. I can actually remember swatting the one that bit me…the next two weeks are the most ill I have ever been, they don’t call it “Break-Bone Fever” for nothing. Other people in the compound we lived in got dengue at the same time. it was only through a concerted coordinated effort of the Landlords and the locals that we managed to stop the spread – Locally – by spraying or “fogging” the area with an unbelievable amount of chemicals. Trying to eliminate/manage areas of stagnant water – other than wetlands – in an urban environment is of a high priority to compliment mitigation efforts in reducing the impact of Dengue

Reply to  MarkWhelan
June 12, 2019 6:51 am

Mark ==> Thanks for sharing your personal experience. Many of our colleagues in the DR contracted dengue — and were usually hospitalized immediately to reduce their risk of serious complications.

Eric Campbell
June 12, 2019 4:12 am

If only there were a vaccine…….


June 12, 2019 5:03 am

I recommend looking at the WHO historical maps of Dengue. It is spreading. Then look at the maps provided above. The areas where it has become established in Australia is First World, the poor are phenomenally wealthy by world standards. It is spreading. It has nothing to do with climate change, and everything to do with travel. As a fresh graduate in Queensland decades ago and long before Dengue came to the region, we used to joke about it, Aedeies mosquitoes used to breed under the hospital.
I helped sponsor a reduction program in one small Indonesian city. Dengue Haemorrhagic Fever was killing the employees kids. When I left, my replacement was not going to take the issue seriously. I took him to the top of the hill, and showed him where the problem existed. It was everywhere. I quietly quoted studies, Indonesian data, and world wide trends. He got the message.
Message. Dengue is not just a third world issue. It is spreading by common travel. Control programs are just that – control. Environmental activists will resist management, until they contract the illness. But it can kill.

June 12, 2019 5:33 am

When I first went to New Guinea DDT had not been denigrated by ratbag greenies, & Australian management & money maintained the spraying program.

They sprayed problem breeding areas, but also sprayed the inside walls of all premises & homes every 6 months. DDT not only kills mozzies, but also is highly irritating to them. They leave sprayed homes very quickly. This was law, no one could opt out.

There were effectively no mozzies. Later after independence all this broke down, & mozzies returned in droves. In our spare parts warehouse we burned 30 mozzie coils all day. Without them it was impossible to work in there at all.

I came back to Oz, basically to get away from Mozzies.

Reply to  Hasbeen
June 12, 2019 9:21 am

Hasbeen==> Thanks for the eye witness account –before and after DDT spraying.

Reply to  Hasbeen
June 12, 2019 10:12 am

I grew up in India in the 50’s and 60’s with DDT sprayed on the walls. A 50lb bag of gammexane (lindane) was in the clinic for treating head lice, When we got a bedbug infestation due to arriving back from a train trip in the rainy season when it was not possible to put bedding out in the sun, the bag was moved to my parents bedroom to conveniently put handfuls into beds and mosquito nets. Malaria (i think P vivax) was treated whenever symptoms occurred, as were ‘tummy bugs’. My Dad and one brother had dengue, and were very sick. I am thankful my girls grew up before they took the lindane out of Kwellada shampoo as the Canadian primary schools were hotbeds of headlice.

Reply to  Fran
June 12, 2019 12:28 pm

Fran ==> Thanks for your experiences in India. People used to be much more sensible about the seriousness of mosquito-borne diseases and what was needed to prevent them.

The US has defeated malaria and yellow fever and has not had endemic dengue — and will not have.

John Mclondon
Reply to  Fran
June 14, 2019 1:42 pm

ivermectin is as effective as lindane for lice without all the toxicity.
Dengue in India is not as it was in the 50s, it has gone up substantially. When I visited there a few years ago, southern states like Kerala had a lot of Dengue cases which was not there in the 70s and 80s.

June 12, 2019 7:07 am

Ya know, this raises the question of the ticking time bombs we have in our exploding homeless communities in urban areas, primarily in temperate climates. They have all the ingredients for an epidemic, dense population packing, environmental exposure, and lack of sanitation. It won’t take much to set one off and then what?

June 12, 2019 9:25 am
June 12, 2019 9:46 am

mosquitoes aren’t a tropical insect.
There are large numbers of mosquitoes above the Arctic Circle, where there are no predators.

Reply to  Neo
June 12, 2019 11:55 am

Neo ==> Yes, of course, mosquitoes can kill full grown mammals in the Yukon. For dengue transmission, the particular species that can pick up and pass on dengue are limited. The map of the United States in the essay shows the current distribution of Ae Aegypti, the primary insect vector of dengue. Note that despite the presence of the vector, dengue is absent.

June 12, 2019 11:52 am


The “spread” or “increased incidence” of dengue will be driven by population increases in the poorer tropical-zone nations. There it will be endemic and epidemic, particularly in the crowded cities and their associated slums. This is a real concern for international health organizations. Development of a safe and effective vaccine would save a lot of lives.

Curtailing CO2 emissions will have a near zero effect on dengue incidence or its geographic spread.

The United States will no have endemic dengue as the two required conditions — plentiful insect vectors and plentiful infected humans — will not co-exist. There will be cases of dengue but they will be among arriving or returning infected persons from areas like Africa and the Caribbean. Despite the continued arrival of infected individuals, dengue will not establish itself here.

Thanks to the many readers who shared with personal stories of dengue infection. It is not pleasant.

# # # # #

June 13, 2019 5:42 am

Ouch! I got bit by a model.

John McLomdom
June 14, 2019 1:31 pm

Vector control is extremely difficult for Dengue since these mosquitos use freshwater and don’t need much water. Because of that, sanitation doesn’t have much influence in controlling it. Removing all containers that could collect water is not going to remove small pockets in trees, plants, etc. Dengue is already spreading in France, Spain, etc with better sanitation.
But is it an admission that earth is warming?

Reply to  John McLomdom
June 14, 2019 7:51 pm

John ==> When I say “sanitation”, I include the idea of picking up the trash, cleaning up the backyards, etc. It is not necessary to eliminate Ae. aegypti to get rid of dengue. Public health just has to knock down mosquito populations and isolate dengue patients. The mosquitoes are not the source of the dengue virus — infected humans are.

Southern France and Spain are seeing dengue cases because of the immigration of infected humans — many of whom move into slum-like poor neighborhoods and refuge-camp like areas.

They can eliminate dengue through serious and sensible public he;lath measures — vector control and isolation of dengue patients in hospitals.

Reply to  John McLomdom
June 14, 2019 7:55 pm

John ==> Don’t be fooled . . . Reunion, France is an island off the coast of Madagascar (not in Europe).

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