AGU: long term global warming not to blame for Zika outbreak

American Geophysical Union says: Combination of El Niño and 2016 Ecuador earthquake likely worsened Zika outbreak

WASHINGTON D.C. — A Zika virus outbreak in coastal Ecuador in 2016 was likely worsened by a strong El Niño and a magnitude 7.8 earthquake that struck the region in April, according to a new study.

A new research commentary suggests the earthquake left more people exposed to disease-carrying mosquitos, and climate variability associated with the 2014-2016 El Niño event created more favorable mosquito breeding grounds. Warmer temperatures and increased rainfall, combined with destruction of the region’s infrastructure and a population influx into large cities, likely caused the number of Zika cases to increase 12-fold in just three months, according to the study’s authors. The research was accepted for publication in GeoHealth, a journal of the American Geophysical Union.

Zika was first observed in Africa in the 1950s and recently spread to South America and Southeast Asia. The disease is transmitted by mosquitoes and usually causes a mild illness with symptoms such as headaches, rash and eye infections. Zika virus infection in pregnant mothers can result in a variety of birth defects. As of September 2017, approximately 6,811 suspected and confirmed cases of Zika have occurred in Ecuador, according to a World Health Organization report.

El Niño is the warm phase of a regular climate pattern that occurs in the Pacific Ocean. It brings warmer air temperatures and higher rainfall levels to the west coast of South America. Previous research established a link between the 2014-2016 El Niño and the spread of Zika in South America, but the new study goes further and examines the interaction between these two events and the 2016 earthquake.

The new commentary suggests changes in the climate can amplify the worst effects of natural disasters and disease outbreaks in socially vulnerable regions. Areas that are already stressed by short-term climate changes like El Niño can be sent over the edge due to a catastrophe and may struggle to recuperate afterwards, said Cecilia Sorensen, a Living Closer Foundation fellow in climate and health policy at the University of Colorado School of Medicine in Aurora, Colorado and lead author of the new study.

The authors studied the effects of short-term changes in Ecuador’s climate, not long-term global warming patterns. But extreme El Niño events such as the one observed in 2016 are projected to increase in frequency due to human-caused climate change. Sorensen’s team suspects that the combination of increased extreme events and long-term warming could lead to conditions that favor the spread of mosquito-borne diseases.

The findings are important because of their applicability to recent events, like recent earthquakes in Mexico and hurricanes in the Caribbean and the U.S., according to Ángel G. Muñoz, a research associate at the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory.

“The main message of the authors is related to the important question of how a combination of natural hazards can increase the vulnerability of the population, making people’s exposure higher and lowering their adaptive capacity during and after the occurrence of such hazards,” he said.

Examining the Zika outbreak

A magnitude 7.8 earthquake struck the province of Manabi in coastal Ecuador on April 16, 2016. The quake affected approximately 720,000 people, destroyed much of the region’s sanitation and healthcare infrastructure, and resulted in a massive influx of displaced residents into urban areas.

The lack of reliable access to water led people to store water around their home, increasing the number of places for mosquitoes (especially Aedes aegypti) to reproduce. Photo credit: Walking Palms Global Initiative

Sorensen and the study co-authors worked with the non-governmental organization Walking Palms Global Initiative to operate a mobile health clinic after the earthquake. They saw many women and children coming in with symptoms typical of mosquito-borne illnesses like dengue fever and Zika. In July of 2016, UNICEF reported the number of Zika cases in Ecuador spiked from 92 cases before the earthquake to 1,106 cases just three months after the event. 80 percent of these new cases occurred in Manabi.

The research team set out to study how damage from the earthquake and short-term changes in weather associated with El Niño could have potentially exposed more people to mosquitoes and exacerbated the outbreak.

“We saw so many people affected by the earthquake that were sleeping outside without any shelter from mosquitoes, so we were worrying that the region’s changing climate could facilitate the spread of diseases,” Sorensen said. “Natural disasters can create a niche for emerging diseases to come out and affect more people.”

Link to climate changes

Sorensen’s team reviewed the existing research on the link between short-term changes in climate and disease transmission. They then applied those findings to explain the role of the earthquake and El Niño in the Zika outbreak.

The researchers suggest El Niño created ideal conditions for Zika-carrying mosquitos to breed and make more copies of the Zika virus. The warmer air temperatures and increased rainfall brought by El Niño have previously been associated with a higher likelihood of dengue outbreaks. Warmer temperatures can accelerate viral replication in mosquitoes and influence mosquitos’ development and breeding habits.

Additionally, the El Niño event brought warmer sea-surface temperatures, which have been shown to correlate with outbreaks of mosquito-transmitted diseases. Estimates from remote sensing data in coastal Ecuador show that sea-surface temperatures were higher than average from 2014-2016.

The team also believes an increase in water scarcity after the earthquake indirectly benefitted mosquito development. The quake damaged municipal water systems, forcing people to store water in open containers outside their homes. These containers served as additional habitats for mosquito larvae to grow in.

The new findings could be used by governments to identify and protect vulnerable communities before natural disasters happen, Sorensen said.

“One idea is to develop disease models that can use existing climate models to predict where these vectors will show up due to climate variability,” she said. “Applying these new models to areas that have pre-existing social vulnerabilities could identify susceptible regions, allowing us to direct healthcare resources there ahead of time.”


This study is open access. A PDF copy can be downloaded at

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October 12, 2017 8:48 am

” In July of 2016, UNICEF reported the number of Zika cases in Ecuador spiked from 92 cases before the earthquake to 1,106 cases just three months after the event.”
…..UNICEF reported they began actively testing and monitoring 3 months after the event /snark

Tom Halla
October 12, 2017 9:00 am

Zika has the same vector as yellow fever, and one reason Philadelphia is not the national capital of the US was an outbreak of yellow fever in the 1790’s. That was [still] the LIA, so I doubt Aedes egypti is all that cold sensitive.

Rhoda R
Reply to  Tom Halla
October 12, 2017 8:17 pm

Not only that, but Ecuador, being on or near the equator, is generally warm anyway. I’d say the earthquake had more to do with the upswing in Zika cases than anything climatological.

October 12, 2017 9:09 am

If their theory is correct, then there should be a corresponding (but smaller) increase in the same diseases outside the earthquake zone. If such an increase exists, then one could theorize that its causes (which may or may not be El Nino) were turbo charged by the breakdown in living conditions and sanitation due to the earthquake. But there is no mention in the article of any such comparison, and I suspect not much changed or the alarmists would have been screaming about it and blaming it on climate change already.

October 12, 2017 9:46 am

Once again, another article about changes in climate with no quantification of that change. It is reasonable to assume that the strong El Nino led to warmer temperatures, but how much warmer than normal? Was there a similar outbreak with the 1998 El Nino? How about strong El Ninos before that? As far as man-made climate change – how much warmer is Equador now than 50 years ago?
My semi-educated guess would be that the weather conditions during the Zika outbreak were not unusual, and that the earthquake and resulting conditions are 99.99% responsible for the outbreak.

Reply to  jclarke341
October 12, 2017 10:55 am

It was the “massive influx of displaced residents into urban areas” that caused the outbreaks. Dense populations in urban environments are breeding grounds for pathogenic out-breaks. There were enough mosquitos already. All that was needed was more fertile fields of warm bodies capable of incubating the viruses for collection by the vectoring mosquitos.
Any event that increased human population density would suffice, be it economic or other cause.

Reply to  rocketscientist
October 12, 2017 3:04 pm

Correct – they act like this is a new phenomenon. The only thing new about it is Zika.

Reply to  jclarke341
October 12, 2017 1:03 pm

It isn’t the warmer weather that is important. It is the rains that always follows a Nino. That means lots of small water bodies suitable for mosquitos, particularly in an area like coastal Ecuador, which normally has a quite arid climate and consequently little or no proper drainage, particularly in smaller towns or villages.
Poor people don’t usually build expensive drains that are only needed for a month or two every several years. Not rich people either when I think about it. You should see what the streets in Dubai City look like after a heavy rain….

Walter Sobchak
October 12, 2017 10:34 am

The theory of spontaneous generation of biological entities was abandoned 125 years ago, as was the theory that diseases were caused by miasmas arising out of swamps.
Mosquitoes will breed in standing water in any climate. Malaria was a problem in Russia and the Great Lakes region of the US, until they began to drain swamps and spray for mosquitoes.
Climate whether colder or warmer has zero to do with the pestilence of mosquitoes or their transmission of disease.
The biggest problem we have with getting rid of mosquitoes and their disease parasites are the watermelons of the “environmental” movement who have renamed malaria swamps as “ecologically important wetlands” and perpetuated the legend that DDT is “bad for the environment”.
We will not be free of the plague of tropical disease until we eradicate the “environmentalists”.

Reply to  Walter Sobchak
October 12, 2017 10:58 am

That’ where the name “malaria” comes from. It began in Venice where the nearby swaps caused stenches in the summers. Mal aria literally means bad air in Italian.

Reply to  Walter Sobchak
October 12, 2017 12:51 pm

Malaria isn’t a tropical disease, you could find it north to the polar circle in Scandinavia back in c. 1850. And no, it isn’t sensible to try and eradicate it by draining swamps. It doesn’t work and it isn’t necessary. When people get decent housing malaria simply disappears. About 150 years ago malaria was all over the US and Europe but it just went away when houses got good enough to mostly keep mosquitoes out in nighttime, breaking the transmission chain.

Reply to  Walter Sobchak
October 12, 2017 1:13 pm

Mosquitoes are if anything more profuse in Alaska than in Florida. And they have less time to suck blood with which to make more.

Reply to  Gabro
October 13, 2017 8:27 am

There may be more mosquitoes but lower temperatures means fewer at the stage in their lifecycle when they can pass on the malaria parasite. Also the lifecycle of the parasite is temperature dependent.

Reply to  Gabro
October 13, 2017 11:54 am

In northern areas transmission was almost exclusively indoors and mostly in winter.

Reply to  Gabro
October 13, 2017 12:00 pm

Malaria was just as prevalent in temperate zones as in the tropics, before modern health and housing. It wasn’t until the end of the 19th century that science even learned how “mal aria” was transmitted.
And even during the LIA, northern cities suffered from mosquito-borne diseases. All the tropics had making the situation worse was the range of some of the worst vector genera.

October 12, 2017 10:35 am
Reply to  Resourceguy
October 12, 2017 1:19 pm

Keeping ahead of viral and bacterial mutations is a never-ending struggle. When new mutations beneficial to the pathogen arise, the population of the strain with it explodes. The fight between natural selection and new drugs will continue indefinitely.

October 12, 2017 11:35 am

No its bad CAGW will be involved somehow, get the team on this immediately.

October 12, 2017 12:43 pm

Aedes aegypti almost never breeds in natural ponds and similar, but rather in man made sites. Rainwater left in buckets or tins or even old car tires are typical breeding sites, so a rainy Nino season and an earthquake that leaves a lot of devastation and general mess plus a breakdown in public water supplies is just about the ideal conditions for it. And, no, it is not a strictly tropical species, but it does require quite warm summers. Philadelphia is just about at the edge of its range:comment image

Reply to  tty
October 12, 2017 2:15 pm

The amount of water needed for Aedes aegypti to lay eggs can be held in a discarded bottle cap. Any wet rubbish pile with trapped water will suffice.

October 12, 2017 7:11 pm

Have been intimately involved with the Zika and prior to that dengue outbreak in the USA I can assure everyone that global warming, El Nino, earthquakes, etc had NOTHING to do with the outbreaks. The World Cup Soccer match in Brazil and modern transportation were the prime reasons Zika came over from Africa to the New World. Aedes aegypti the primary vector (also possibly vectored by Aedes albopictus) was/ is causing problems in Brazil. Both species are tree hole/ container domestic mosquitoes. Domestic meaning they long ago adapted to living with humans. One of the biggest problems with Zika was that a large percentage, not as large as the media reported, got the disease but were asymptomatic. That meant they could get on a airplane infected with Zika and in a few hours go from Africa to Brazil and Brazil to the USA. All it would take once here is a bite from aegypti and transmission is then possible. What Zika, and several dengue outbreaks before Zika, taught us is that arthropod vectored diseases once common in the USA before WWII could be here over night. Six months ago Brazil was having a yellow fever outbreak in several small western town cities. The fear was it would make it to one of their larger cities. The whole emerging disease argument by the CAGW crowd is as much fantasy as more intense and numerous hurricanes. I would note significant dengue outbreaks in Puerto Rico are probably going to happen in the next six months to a year. Hurricane Maria played a role only in destroy infrastructure and reducing mosquito control capabilities. Also more people will be living outside screened enclosures.

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