The Perfect Storm: Climate Change and Zika Virus Disease

This post originally ran on NACCHO’s Healthy People, Healthy Places blog. For more environmental health news and information, visit 

By Andrea Grenadier, Communications Specialist, NACCHO

Aedes_aegypti_biting_human-300x238If you were writing a popular novel designed to terrify, you could hardly come up with a better plot device than introducing Zika virus disease. A perfect storm of a vector-borne disease, its kaleidoscopic facets are staggering in number and touch on a multitude of aspects—lack of sanitation and rampant urbanization, reproductive rights, access to prenatal healthcare as well as abortions, government instability, religion, possible sexual transmission, the politics of pesticides, the upcoming summer Olympic games in Brazil, rampant inequality and lack of public health infrastructure, poverty that roots families in place with few or no options, and perhaps one overarching villain: climate change.

The rapid spread of the Zika virus is an international public health crisis, and possibly responsible for birth defects including microcephaly, as well as an increase in cases of Guillain-Barré syndrome, a rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. The mosquito Aedes aegypti—the species that also carries dengue and chikungunya—is the vector, and is found in warm, humid areas in Central and South America, Mexico, and the southeastern United States, among other regions. The numbers growing daily show the sheer breadth of the disease: There could be up to four million cases this year, just eight months after the first case was reported in Brazil. There are30 countries with active virus transmission. As of February 24, there were 107 confirmed cases of travel-associated Zika virus disease in the United States.

The sweep of activity around Zika virus disease seems unprecedented, even considering the Ebola response. Last week, a team of scientists from two Texas hospitals have come up with the first rapid testfor the Zika virus, allowing doctors to potentially diagnose the disease in just a day’s time. Previous Zika virus tests took as much as a month to yield results, but the test, developed by Houston Methodist and Texas Children’s hospital researchers, is the first hospital-based rapid test in America.

Along with the need to strengthen public health systems, Zika virus is a complex challenge. The World Health Organization launched a $65 million global Zika response plan. Where is climate change?

Scientists understand that it’s the heavy rain and heat that assists A. aegypti in breeding and spreading, and climate change could play an even heavier role in the escalation and proliferation of the disease. The Washington Post reports that “in recent years, researchers have increasingly devoted themselves to the investigation of how future climate scenarios might affect these mosquito populations. And many have concluded that a warmer world is likely to be a boon to the bugs, allowing them reproduce faster, emerge earlier in the season, survive longer and even spread northward.”

An influential 2005 paper, “Climate Change and Human Health,” by the late Paul Epstein of Harvard Medical School, cites mosquitoes’ sensitivity to temperature changes, causing these vectors to bite more, breed more, and consequently, spread more disease. Although climate change is a likely spur, it is hard to define precisely how climate change drives the spread of Zika and other vector-borne diseases. In a 2013 paper in Environmental Health Perspectives, the paper “Climate and Dengue Transmission: Evidence and Implications” examined the effects of climate factors on dengue and its Aedes vectors, and found that even as they acknowledged that climate affects vector dynamics, agent development, and mosquito/human interactions, the ultimate impact that climate will have on transmission is unclear.

Both NACCHO and the Big Cities Health Coalition support President Obama’s $1.8 billion emergency funding request designed to prepare for and respond to the Zika virus. Local health departments are ramping up their activities and engaged in educating the public and healthcare providers about Zika, conducting prevention activities via mosquito eradication, and screening travelers from countries and territories with active Zika transmission. Emergency measures can only take us so far; we need more sustained funding, including research into vaccines and surveillance, which many states can no longer afford to conduct. Health department staff increases on the local level are also critical to respond to this and other emerging infectious diseases, which are more likely to come as the effects of climate change make their relentless way to the United States.

See what local health departments need to know about Zika virus and follow NACCHO’s ongoing Zika coverage.

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