Claims of Warming-Aided Vectorborne Diseases: a Follow-up

Guest Essay by Kip Hansen


follow-up_tickLast week I wrote about the latest CDC report on the increased incidence of vectorborne diseases in the United States.  The report was misrepresented by the magazine Science News whose report depended entirely on an article in the New York Times titled: “Tick and Mosquito Infections Spreading Rapidly, C.D.C. Finds”.    The Science News piece echoed the New York Times’ journalist  Donald G. McNeil Jr.’s  claim that “Warmer weather is a major cause for the explosion in these vector-transmitted diseases, The New York Times reports, as ticks thrive in areas once too cold, and mosquito populations mushroom during heat waves.” (the link to the NY Times article is original in the Science News piece.)

The actual claim made in the NY Times was this:

“Warmer weather is an important cause of the surge, according to the lead author of a study published in the C.D.C.’s Morbidity and Mortality Weekly Report.”

Sharp eyes and critical minds can see already that the original NY Times’ claim of warmer weather being an “important cause” has been elevated by Science News  to be a “major cause” and the NY Times’ “surge” has been magnified into “the explosion”.

I reported here that the CDC research report under question does not contain the words “warming” or “warmer” or “weather”,  nor does it contain the words “climate” or “climate change”.  The official spin-off factsheets and public information materials also contain no mention whatever of global warming, warmer weather, or climate change.

Having used a certain journalists’ trick myself many times, I suspected the McNeil of the Times had done the same, but with a particularly (in my opinion) unethical twist.  The problem is that the CDC report does not blame global warming for the increased incidence and geographical spread of mosquito- and tick-borne diseases, yet the Times (McNeil) wants to say that.  McNeil then either telephones or emails one of the authors of the report, asks some leading questions, and turns the answer(s)  into  this  “crypto-quote” — “Warmer weather is an important cause of the surge, according to the lead author….”.  The crypto-quote gets picked up by Science News and is magnified into “Warmer weather is a major cause….”.

CRYPTO_QUOTE:  an attributed statement that is not a direct quote but rather a paraphrased statement, often derived from the answer to one or more undisclosed questions.  Crypto-quotes are nearly impossible to refute as the question(s) used to elicit the response is withheld along with the actual words used in that response.  A crypto-quote is then simply a journalist’s interpretation of an unknown response to an unknown question.

My question in all of this was:

“How did this misunderstanding come about [?]– two major news sources, one an “international newspaper of record” and one a sub-set of one of the world’s leading science journals have both claimed that your team identified “warmer weather” as a major cause of “the explosion in these vector-transmitted diseases.   I am hoping for a clarifying statement that I can quote.”

I posed this exact question to Dr. Ron Rosenberg, Division of Vector-Borne Diseases/CDC, who was listed in the study as the Corresponding Author and is the Associate Director for Science at CDC’s Division of Vector-borne Diseases.

Here is his reply:

“Thanks for calling this to my attention. I haven’t read or heard any of Dr Petersen’s interviews as division director so it would be best if you seek clarification from him; I’m copying some CDC people who should be able to arrange that. 

You are correct that the MMWR article did not mention any specific role for climate in the increase in cases. Doubtless changes in climate affect transmission but the relation is complex and not well understood. For example, while Lyme cases seem to be increasingly reported from farther north over the last decade, they’ve been moving west and southward as well.”

[Lyme cases could not move further east from their origin — Connecticut/Rhode Island —  as that way lies the Atlantic Ocean.]

True to his word,  Dr. Rosenberg cc’d his response to several colleagues at CDC, including Kate Fowlie,  CDC Press Officer, who offered this additional response:

Thank you for reaching out.

Dr. Petersen has said that the increase in diseases caused by the bite of an infected mosquito, tick, or flea in the U.S. is likely due to many factors, and changes in temperature is likely one of them. 

Other factors include:

  • Spread of pathogens

Mosquitoes and ticks and the germs they spread are increasing in number and moving into new areas. Infected animals can also contribute to spread of pathogens into new areas.

  • Travel and commerce

Overseas travel and commerce are more common than ever before. A traveler can be infected with a mosquito-borne disease, like Zika, in one country, and then unknowingly transport it home.

  • Newly identified or newly introduced pathogens

Finally, new germs spread by mosquito and tick bites have been discovered and the list of nationally notifiable diseases has grown.

  • People’s behavior

People are outside more often in warmer weather and are more likely to get bitten.

Dr. Petersen spoke at the telebriefing last week and the transcript is available online here:

In Kate Fowlie’s follow-on email, we finally see the “warmer weather smoking gun”  — the CDC says officially (note that Kate is copy-and-pasting from the Factsheet)  “People are outside more often in warmer weather and are more likely to get bitten.”

As suspected, this innocent obviously-true little tidbit has been spun and magnified first into an “important” cause and then re-magnified into a “major” cause of the increase and spread of vectorborne diseases.   The CDC’s  warmer weather means just what it does to you and I — when the weather is nice, we tend to go out — many of us to local parks and woods  and many more of us into our yards — where we are more likely to encounter biting mosquitoes and nasty little ticks.

For those with a real interest in vectorborne diseases and what the CDC had to say about them, I recommend reading the transcript of the CDC’s telebriefing of the media on the topic.

There are, of course, many ways in which temperature differences affect biological vectors (mosquitoes, ticks, fleas), disease transmission and geographical spread of these diseases — for instance, high temperatures can cause mosquitoes to mature faster and cause infected mosquitoes to become ‘more’ infectious.  As Dr. Rosenberg correctly points out, ”the relation is complex and not well understood”.

Ron Bailey, at, covered this story from a slightly different viewpoint in his blog post Over-Regulation Is Making Us More Vulnerable to Disease”.  (h/t Roger Knights).

Late addition:  9 May 2018 2200 hrs Eastern Time

A dated but well-rounded view of this topic can be found in this paper from 2001:

Climate Change and Mosquito-Borne Disease

by Paul Reiter — Dengue Branch, Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, San Juan, Puerto Rico

The paper begins with this:

“The earth’s climate has always been in a state of change. For nearly three centuries it has been in a warming phase. This was preceded by a cold period, the Little Ice Age, which was itself preceded by a warmer phase known as the Medieval Warm Period, or Little Climatic Optimum. Such changes are entirely natural, but there is evidence that in recent years a portion of the current warming may be attributable to human activities, particularly the burning of fossil fuels. The potential impact of this global warming on human health is a major subject of debate.”

and ends with this:

“Final Comment

The natural history of mosquito-borne diseases is complex, and the interplay of climate, ecology, vector biology, and many other factors defies simplistic analysis. The recent resurgence of many of these diseases is a major cause for concern, but it is facile to attribute this resurgence to climate change. The principal determinants are politics, economics, and human activities. A creative and organized application of resources is urgently required to control these diseases regardless of future climate change.”

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Author’s Comment Policy:

The use of what-I-have-dubbed crypto-quotes has led to a lot of flawed news and is a feature of lousy journalism.   It is one thing to honestly summarize a speech into a few lines of journalism, as long as the original speech is available and linked.  It is another thing entirely to paraphrase a response to an unrevealed question in a way that puts words not spoken into the mouths of others.  The later is simply unethical.

This essay is about Science Journalism — not climate change or mosquitoes.

[Just in case: it is not about coyotes either!]

Always happy to read and respond to your comments here or you can email me at my first name at the domain i4 decimal net.

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Tom Halla

It looks as if the CDC does not want to directly state that they were misquoted.


From my experience the rank and file CDC scientists are professional and not seeking publicity.
Several years ago I was presenting at a Lyme conference and thought we might get some publicity out of it. Instead, the CDC accidentally wrote into their abstract that the true incidence of Lyme was 300,000+ cases per year. One they realized their mistake and that the number was going public, they prepared a hasty press release that dominated coverage. They weren’t seeking the limelight or looking for headlines. I have a very hard time imagining any of them jumping onto this climate change headline grabbing bandwagon.

Great article Kip, thank you.
When I used to write for the newspapers over a decade ago (typically countering global warming extremism and green energy nonsense), the editors almost never changed a word of my text because it was too technical for them, but they almost ALWAYS changed my titles.
The worst example was comical – Maurice Strong had bought a house in Ottawa and was reportedly going to be an adviser to Prime Minister Jean Chretien.
I wrote an article entitled “Strong Reservations”, which I thought was rather clever.
The article was published as written in a major Canadian newspaper, but with the possibly stupidest title in journalistic history – I have difficulty recalling the details, but the title was something like “Maurice Strong is a silly old Po-Po head”.
How embarrassing!
One can only hope that readers understand that authors’ suggested titles rarely escape the editor’s hatchet.


No doubt the two articles in the NYT and Science News will be in contention for a Pulitzer prize this year.

“If it bleeds, it leads.”
Its a ticking time bomb!’
Tick tick tick …


Exploit fear to create drama = lots of clicks. That’s “journalism” in 2018.

John M. Ware

A very small chicken has been termed a “Pullet Surprise.”

Jim Veenbaas

Just an excellent, excellent article. Illustrates the way the media can manipulate facts. Great stuff!!


As I keep saying, every days a school day at WUWT. I expected to learn about climate change when I first visited. Never did I expect to learn about politics, religion, renewables, coal, oil, fracking, EV’s, disease, insects and journalism, to name but a few subjects.
Oh! I forgot to mention trolls, I also learned a lot from Griff etc.

Based on the fact that ticks are so much worse in warmer regions of the USA, and tick-borne diseases were first identified in warm regions, this makes perfect sense.
Lyme disease (Lyme, CT):
Rocky Mountain Spotted fever (Idaho and Montana):
Oh, wait…
In general, the effect of an increase or decrease in temperature can be estimated by examination of a growing / hardiness zone chart, like this one for the United States:
If you compare the scale-of-miles to the zone sizes you can see that a 1°F change in temperature is equivalent to a shift in latitude of about 30-40 miles — barely noticeable.
From the rule-of-thumb in Hansen 1988 (“A warning of 0.5°C… implies typically a poleward shift of isotherms by 50 to 75 km…”) we get 34.5–51.8 miles per 1°F change in temperature, which seems a bit high.
(But the zone shift might be a little more than that, since hardiness zones are mostly determined by low temperature extremes and freeze timing, and global warming is predicted to mostly increase nighttime lows in winter, with little effect on summer highs.)

I grew up in Michigan. The mosquitoes up there were terrible — much worse than they are here in North Carolina, where the climate is milder.
I also lived for a time in the Bay Area of California, where the climate is milder yet. There were even fewer mosquitoes, there.
They say that in Alaska the mosquitoes are even worse than in Michigan — much worse, in fact: image
Yet climate hysterians insist that a slightly milder climate, due to anthropogenic climate change, will worsen our problems with mosquitoes? It is amazing to me is that anyone at all believes such obvious nonsense.
The problem with common sense is that it is so very rare.


Not too many mosquitos in Scotland. The midges are too vicious.
A preferred repellent is garlic.
Nuff said!
~Come Egor, let us take our leave, the sun is rising~


I encountered the worst mosquitoes on a woody camp ground somewhere in the southern part of BC. They were ferocious. The guy who collected the money came completely sealed up in a bee farmer’s costume. You could watch the mosquitoes frantically squeeze through the window screens even though our windows were kept closed. If you left your camping van you’ld instantly be covered in mosquitoes that were crazy enough to bite you through the little aerating holes in your sneakers , through your jeans plus underwear and thick wool pullovers over shirts. Just crazy many very hungry mosquitoes. The place was singing with mosquitoes.
A bunch of cyclists arrived and started to pt up their tents. After maybe fifteen minutes they packed up again and left -and I’m pretty sure they didn’t even notice the two black bears patrolling the camp ground. We just sat and watched the dancing cyclists. It was kind of fun. For one night.

Sweet Old Bob

People are catching on to this sort of stuff . The alarmists are discrediting themselves .
Yay !

Fake News tells us that every bad thing in the World is caused by CAGW and Global Warming, but we have noticed that this is not true now.

NW sage

Since warmer (better) weather often results in our being outside more and therefore bitten more then it follows that if the weather is REALLY warm – as in catastrophic ‘climate change’ warm – we will remain inside more because it is much more comfortable, get bitten less, and all those worrysome diseases will disappear! Is my reasoning valid?

Gary Pearse

I’ve commented on vectorborne diseases and climate to point out that workers who dug the Rideau Canal,which is between between Lake Ontario and Ottawa, after the War of 1812 with the United States died in numbers malaria and this was during the Little Ice Age. Other accounts also mention yellow fever.
Parts of Europe had malarial areas, too. Shouldn’t experts and interested laypersons know this?

Smart Rock

When I first read that about malaria killing people who dug the Rideau canal, I thought to myself: Malaria? In Canada? I wonder if “malaria” was used as a euphemism for the effects of STDs and bad whisky?
The only people I know in Canada who’ve had malaria, caught it in the tropics. And it isn’t as though we’ve eliminated mosquitoes or their breeding areas. I’ve spent enough time doing field geology across Canada, and I’ve had enough mosquito bites to sink a (canoe?). And not only have I never had malaria, but in our safety-obsessed world, I’ve never even been warned about malaria as a hazard.
So I still wonder.


Smart Rock – you only get malaria if an Anopheles mosquito bit someone with malaria a week or so before biting you. You might be able to get malaria if you are rock prospecting around an airport in Ontario if you let enough Anopheles bite you, but in general, North America does not have a good reservoir of malaria (i.e. a lot of people infected with malaria). It once did and it still has lots of competent vectors. You should be much more worried about getting West Nile, Jamestown Canyon, an Equine Encephalitis or a half dozen other mosquito-borne viruses with animal reservoirs that are still transmitted in Canada.


Q: What do you get if Typhoid Mary and Sir Edmund Hillary had a baby?
A: Don’t be silly! Everyone knows you can’t cross a vector with a scaler!


Did you contact or send the responses to the journalists, editor or use the complaint box?


As an anecdote, I grew up playing in the outdoors my entire childhood, played in fields/creeks/swampy areas, must have gotten thousands of mosquito bites.
Then I went to work as a land surveyor, pretty much the same thing, playing in fields/creeks/swampy areas, with the added risk of highly populated areas and some really nasty alleys.
I’m still here, I’ll put it down to luck and a robust immune system built up over time.
Dare ya to prove me wrong 🙂


The two examples sited in this post illustrates the reason I began my efforts to educate myself with regards to the actual facts about climate change. I would like to thank you Anthony and all of individuals who have been posting on this site as well as all of many people commenting. Many of my friends and acquaintances have relied upon me to help them understand various scientific topics. I am one of the few people they know with a college degree. Being able to answer a relatively complex question on a level they could understand required me to obtain as deep an understanding as possible. It would not have been possible for me to do this without the efforts of all of y’all.
Thank you

Crispin in Waterloo

You are what is called a maven. The independent investigation of truth is a solid base for society. It is the capacity to understand for oneself that makes the world recover from its occasional loss of sanity.

Crispen, Crowcane: If only more people understood what it takes to be a maven.


From the article: “The CDC’s warmer weather means just what it does to you and I — when the weather is nice, we tend to go out — many of us to local parks and woods and many more of us into our yards — where we are more likely to encounter biting mosquitoes and nasty little ticks.”
Warmer rather than cooler, rather than warmer than last year. 🙂


Great detective work unmasking the propaganda in these NYT/Scince News articles. I laughed when you uncovered the origin of the “warmer” quote.
The writers must have thought noone would check up on them..

I would note that, re Ron Bailey’s excellent piece, these “journalism” pieces are always linked. There are articles to be found on all of the “climate change” advocacy sites that attack any kind of GMO, attack vaccines, attack pesticides – everything that can actually reduce the incidence of pestilential diseases.


“over the last decade, they’ve been moving west and southward as well.”
Surely if the spread was caused by warming the spread would be moving northward.

Thanks for all the great work, Kip. But I had to point out your coyote admonition to my wife. She said ticks like coyotes.

Kristi Silber

Did you read the study, Kip?
“Vectorborne disease epidemiology is complex because of environmental influences on the biology and behavior of the vectors. The longevity, distribution, biting habits, and propagation of vectors, which ultimately affect the intensity of transmission,, depend on environmental factors such as rainfall, temperature, and shelter. ”
Temperature is important. One might even say it’s a major factor in the epidemiology of the diseases. That doesn’t mean there aren’t other major factors, though, operating in different ways and on different scales. Whether climate change has affected spread isn’t clear, and you are right to say that it’s not warranted to say that temperature is responsible for the surge.
However, neither its it good journalism to go form the CDC emails to this:
“In Kate Fowlie’s follow-on email, we finally see the “warmer weather smoking gun” — the CDC says officially… “People are outside more often in warmer weather and are more likely to get bitten.”
“As suspected, this innocent obviously-true little tidbit has been spun and magnified first into an “important” cause and then re-magnified into a “major” cause of the increase and spread of vectorborne diseases. The CDC’s warmer weather means just what it does to you and I — when the weather is nice, we tend to go out — many of us to local parks and woods and many more of us into our yards — where we are more likely to encounter biting mosquitoes and nasty little ticks.”
The media don’t have access to your emails, so they couldn’t use them for spin. And you completely ignore how Fowler’s statement begins:
“Dr. Petersen has said that the increase in diseases caused by the bite of an infected mosquito, tick, or flea in the U.S. is likely due to many factors, and changes in temperature is likely one of them. ”
You did not interview Dr. Peterson, and don’t know how closely his statement was paraphrased.
How can you even say the paraphrase about warming and surge was wrong? This is what I never understood from your last article. It could have been, but it’s impossible to know, as far as I can tell.
Maybe I’m missing something, but it seems that in this article you don’t even make it clear that it was a statement that led to the “surge” idea, not what he wrote, and certainly not what the emails said.
The CDC article may have been spun by NYT. But don’t you see that you do so, too? You took temperature, which is a fundamental factor in epidemiology of zoonotic diseases, and simply turned it into a human behavioral variable. It doesn’t even make sense. What reason do you have to think that people have been getting more active outside in an expanding range over the last couple decades? Are we back to the idea that climate change is a good thing, we’ve just been slack with the bug spray?
I, too, am writing about journalism, not about climate change. I am writing because I think you are just as guilty of spin as the NYT, and need to be called on it. That was my whole point when I commented on the last article, too.
I like you, Kip. Sounds like you lead an interesting life. You have always been nice to me (a bit condescending, but I can sound that way, too), and I intend no offense in what I say. I believe there is far too much divisive rhetoric concerning climate change, but then catch myself spouting it, too – and then it’s too late to change it! We humans are a fallible bunch.

Kristi Silber

Errr, why don’t I read the thing before posting?
” Whether climate change has affected spread isn’t clear, and you are right to say that it’s not warranted to say that temperature is responsible for the surge.” should be, “Whether climate change has affected spread isn’t addressed by the research.”


“Dr. Petersen has said that the increase in diseases caused by the bite of an infected mosquito, tick, or flea in the U.S. is likely due to many factors, and changes in temperature is likely one of them.”
“Changes in temperature” could mean “warmer and cooler”, instead of your assumption of warmer. That is your assumption isn’t it?


Lyme disease awareness has increased in the UK – so diagnosis rates have probably increased, as well as the likely actual number of cases. But this is down to the uncontrolled population of (mostly introduced) deer in the UK. It is obviously unlikely a warming climate is a factor, since the ticks and the disease were already well established historically in parts of Scandinavia and Continental Europe which are both massively colder than the UK on average. Again the main factor is deer (and their ilk) and suitable habitat near populations.
Endemic Malaria (aka Marsh fever) was historically speaking, only relatively recently eradicated from the UK, the main factor not being climate change, but the draining of marshes near populations of people, and the rise/use of medication that reduced the population infection rate below a sustainable transmissible level.
Minor Resurgence of malaria in Europe and other places has been down to large numbers of refugees, not climate – as covered in this WHO document which does not appear to mention climate change.

Particularly Ixodes ticks are little affected by climate or weather, other than desiccation being the primary abiotic cause of death. Ticks travel tens of meters in their lifetimes, primarily up and down their questing site to re-hydrate.
Ticks are opportunistic travelers, notably on migrating birds.
If I recall correctly, some of the oldest and most respected research on ticks is from a center in northern Siberia, which name escapes me.


We had some exceptionally hot weather and drought around here in about 2012 and the ticks practically disappered. They have made a rebound since then. I’ve been seeing a lot of them this year, which has had a relatively wet first few months.
What’s better: No ticks or green vegetation? I think I prefer green vegetation and will take my chances with the ticks.

That’s an interesting anecdotal observation. Tick activity would have to have been monitored year around for some years to give it validity. Ixodes ticks have two activity peaks, the first in early spring and then in late summer.

Tom Kennedy

One reason that mosquito populations are increasing at an exponential rate is that the primary way nature controls mosquito populations is healthy bat communities are being devastated by industrial wind turbines.
Here is a link to an excellent tutorial on calculating mosquito population growth:
– Birds and bats are being killed at an astonishingly increasing rate as the number of industrial wind turbines increase. (conservative estimate 4 million bats killed between 2012-2016)
– Mosquito populations are rising at an alarming rate.
– Bat kills in one location can impact locations thousands of miles away.
– Bats are long lived and slow to reproduce. Scientists are worried that some of the most useful bat species (e.g. Hoary bats) will not recover and become extinct – Fatalities at wind turbines may threaten population viability of a migratory bat
– Birds and bats provide a natural way of keeping mosquitoes and other problem insects (e.g. Lyme disease ticks) in check.
– Mosquitoes spread diseases like Zika, Malaria, and West Nile Virus. These diseases are spreading throughout the US and Europe.
– Communities are beginning to increase chemical spraying, including aerial spraying of Naled over millions of acres in the US. Naled is toxic to bees and butterflies. The European Union banned Naled in 2012, citing “potential and unacceptable risk showed for human health.”


Surely there are human behaviour factors at work: forests have been substantially restored in parts of the U.S. and other countries; hiking or running in wild forests is encouraged as part of a lifestyle committed to fitness or spirituality; boomers tend to have a Disney faith that there is really nothing all that dangerous in the forest (and indeed, animals that prey on humans have not come back as much as other creatures have); mosquito and tick born diseases attract more awareness, and are now one of the nastier threats you are likely to encounter, instead of being somewhere in the bottom half of the top ten.


Apparently warm weather can be harmful to your health. Authorities should issue warm weather alerts: “Warning – warm weather is forecast — please stay indoors”.


Black Death might have spread by human fleas or lice, without aid of rats:
It’s also thought that direct human to human pneumonic transmission through droplets in the air was possible for that strain of Y. pestis.
Justinian plague might have been spread by Huns or other steppe nomads, not brought by Egyptian rats. Vector unclear, but maybe horse or human fleas or lice.


First when West Nile showed up and then with outbreaks of dengue in Texas and Florida there were some in CDC who played the CAGW card and even said basically you ain’t seen nothing yet wait until it gets even warmer. Wise people in the professional mosquito control community went quietly nuts. They reminded CDC that yellow fever, dengue, and malaria were common diseases in the USA basically up until World War II and the development and refinement of mosquito control techniques. CDC quietly corrected their hyperbole. I don’t remember actually seeing retraction but they changed their webpage, etc. CDC and mosquito control is still concerned with the long established diseases in Africa and elsewhere migrating to the USA especially. Read about the history of Aedes aegypti, the yellow fever mosquito. Its spread took place on sailing ships and during the Little Ice Age.

“Peter Gething of the University of Oxford compared a map of the range of malaria in 2007 with one from 1900, when the world was 0.7 °C cooler. He found the proportion of Earth’s landmass where malaria is endemic has fallen from 58 per cent to 30 per cent (Nature, vol 465, p 342).”


What has aided tick-borne diseases is that Americans are not killing the deer.


not being an epidemiologist I can’t be an authority but the spread of Lyme disease looks to me like what one would expect with a new disease. its spread also appears to correlate with conspiratorial speculations that it came from that Plum Island off of Connecticut where bacteriological warfare research was taking place. If it was just the increase in deer populations mixing with advancing suburbs or one would think it would take place simultaneous with the expansion of suburbs rather than advancing from one section.
[?? .mod]