Climate Change Is Spurring Zika Virus Epidemic, Say Scientists

 

(3BL Media/Justmeans) - Some scientists are calling the El Nino weather that is barreling through Latin America an indicator of what’s to come in the future. And that’s particularly worrisome because the Zika virus’s epic spread in recent months is considered an offshoot of changing weather patterns.

A couple of years ago, when scientists picked up the indicators of a looming El Niño Southern Oscillation (ENSO – the scientific acronym for the warm, eventually rainy conditions we call El Niño), some predicted that global warming and climate change could intensify the phenomena. That’s because the Pacific warms faster as a result of global warming, said climate modeler Wenjun Cai, who was one of a team of researchers that looked at the intersection between El Nino/El Nina and climate change and published a paper on the topic in 2013.

By “making it easier to have maximum SST (sea surface temperatures) in the eastern equatorial Pacific,” Cai told ClimateCentral.org, it was reasonable to expect “more occurrences of extreme El Nino events.”

Climate Change and El Niño

Since 2014, researchers have had their eye on the anticipated impacts of ENSO as it has spanned out across the globe. The emergence of disease epidemics of mosquito-borne malaria and bacterial infections like cholera were considered likely in places like West Africa, where bursts of hotter than usual weather and humid conditions were likely. In June 2014, the International Research Institute for Climate and Society (IRI) issued a warning to vulnerable areas to be ready to respond to ENSO-related events. 

“[In] areas where El Niño may be associated with diminished health risks, diligence in disease control should not be reduced in any way,” warned researchers, who highlighted increase risk for malaria in areas affected by rising median temperatures, rainy conditions followed by drier weather.

But what they didn’t expect was that it would be in El Nino’s back yard, in the hotter than usual terrain of Brazil and Ecuador that would become the initial vector for a mosquito-borne disease that until this century, had rarely been seen in the Americas.

Brazil - The Zika Virus' New Vector

But why Brazil? What does climate – and global warming – have to do with the spread of the Zika virus?

Amy Y. Vittor, an assistant professor at the University of Florida explained it this way in a recent article in RawStory:

The first stage that is needed, is an ideal environment for mosquito infestation a setting that is not only accompanied by humid countryside, but human habitation. Vittor says her team found that “deforestation followed by agriculture and regrowth of low-lying vegetation” offered an even better setting for the mosquito’s survival than the thick, sparsely populated Amazon forest.  She explains these stages of development of an epidemic in layers, whose effects are gradually compounded.

The next layer is dense urbanization and an introduction of impoverished communities, where due to economic factors, sanitation may not be sustained.

Furthermore, says Vittor, “climate change may raise the temperature and/or humidity in areas that previously have been below the threshold required for the mosquitoes to thrive.”

Next comes the expansion of the mosquito vector of the Aedes aegypti mosquito through global travel, warming temps and other factors like inconsistent mosquito eradication efforts. The dramatically expensive World Cup soccer match and an international canoe event Brazil in 2014 offered perfect vehicles for expanding the mosquito’s range of habitat. Economic challenges and a decrease in mosquito control following the events likely added to insect’s spread.

The third layer, of course, is a sizable population of vulnerable hosts that haven’t been exposed to the virus. Ironically, the same year as the virus was thought to have been introduced to Brazil, scientists and health care workers were told to be on alert for mosquito-borne viruses in areas of West Africa where malaria epidemics weren’t common and could spring up “in populations with low or no immunity to the disease.”  

The fourth layer, says Vittor, is the introduction of the virus itself, through air travel and  the various environmental factors already in place.

“When these multiple factors are in alignment, it creates the conditions needed for an outbreak to start,” says Vittor.

If there is any positive takeaway to be found in the tracking of diseases like the Zika virus, it may be a better understanding of the impacts of our climate and the changing environmental landscape. Climate change, scientists are finding, isn’t an isolated phenomena. And as Vittor notes with her expanding research into other mosquito-borne viruses that manage to travel the global landscape, neither is the Zika. 

Addressing the Zika virus won't be easy, but it won't be cheap, either. Cost estimates for the latest epidemic of dengue (another virus spread by the virulent Aedes aegypti mosquito) ran close to $10 billion globally. And not surprisingly, undeveloped countries are the hardest hit. According to a report published by Bloomberg View, of the 10 countries most impacted by a dengue epidemic that ended in 2013, 9 are developing. Brazil with a population of more than 200 million, had the third-highest aggregate cost of all. Epidemics are an expensive "business."

Images: JentaveryAgencia Brasilia