Zika is a mosquito borne virus that is spreading explosively in the Western Hemisphere – and climate change may play a role in its spread. While public attention has been focused on the microcephaly that may be associated with the infection – and the need for contraception among the millions of Catholics who have been advised to avoid pregnancy – the Zika epidemic also teaches important lessons about how other climate-fueled infections may play out in the future.
The Zika virus is transmitted by the Aedes mosquito, which thrives in warm weather and lays its eggs in standing water. This is the same mosquito that carries Dengue, Yellow Fever, and Chikungunya, and it has spread in range to significant portions of the southern US.
The symptoms of Zika virus are less severe than Dengue (known as “breakbone fever”), which infects millions and is rapidly spreading in all regions, but it may be linked to the severe birth defect microcephaly, as well as a serious autoimmune syndrome, Guillain Barre. The World Health Organization has declared the Zika epidemic a public health emergency, and health officials expect the virus to infect millions before the year is out.
For Zika to spread, the mosquitoes that spread the virus need to be thriving. Put simply, climate change benefits mosquitoes because hot weather is good for them.
In South America, where the Zika epidemic has flourished, temperatures are hotter than normal. Some of that is because of climate change. 2015 was the hottest year on record, in South America as well as globally. A strong El Niño year has contributed to heavy rains and flooding in Southern Brazil, and dry conditions in the North. (Although somewhat counterintuitive, dry conditions can create favorable conditions for mosquitoes, because people tend to collect water in containers near their homes, unwittingly creating perfect microenvironments in which mosquitoes can lay their eggs.)
The spread of the Zika virus is complex, and has benefited from such disparate factors as global trade routes, urbanization, deforestation, and World Cup mania – the virus may have been first brought to Brazil by a fan attending the 2014 World Cup. Although scientists acknowledge that climate change may be a factor in the virus’s spread, no one is yet willing to say for sure that climate change has made Zika virus worse.
But even if we don’t know to what extent climate change has fueled the Zika epidemic, Zika already raises many questions about the nature of the public health threats that are likely to unfold because of climate change in the future.
- There is a lot we don’t yet know. This outbreak came as a surprise to many. The potential link to microcephaly, a rare disorder, was not clear until millions were infected. As climate disruption interacts with globalization and deforestation to alter the ecology of vector borne diseases around the world, we can expect to be surprised again by future epidemics.
- Climate change will harm poor communities worst and first. Lest anyone has ever wondered what it means to say that climate change is a justice issue, I suggest examining predictions about the spread of the Zika virus. In the US, experts don’t expect Zika to spread because we have window screens, air conditioning, paved streets, running water, mosquito control programs, and disease monitoring systems. In regions without these amenities, it will be harder to break the transmission cycle. As climate disruption fuels other infections, we can expect to see a similar pattern of impact. Zika virus isn’t fair. The same is true for climate disruption.
- Unintended consequences. The Zika outbreak raises questions about how to address future climate-related disease outbreaks. Right now, massive campaigns are being launched in dozens of countries to kill mosquitoes with chemical insecticide. These campaigns will expose millions of people, not to mention forests, waterways, and other animals, to insecticides. What are the health impacts of those chemicals? If we deploy industrial chemicals on a massive scale to break virus transmission, will rare but serious health impacts emerge? And how can we weigh the benefits against such potential unintended consequences.
- Importance of international cooperation. Dozens of countries must coordinate within a global public health infrastructure in order to effectively respond to a fast moving epidemic to which no one in the Western Hemisphere has immunity. Zika is a dry run for the kind of complex climate-fueled health-related impacts we will see in the future.
- Zika as an opportunity. Zika is on the mind of every public health professional in the Western Hemisphere, and every news-watching woman of childbearing age. Travelers are wondering what to do. People are talking about it, and worried. In the midst of the heartbreak of microcephaly, this makes the Zika epidemic an opportunity to dedicate resources to preparing for the health impacts of vector borne diseases in a changing climate. This means investing in detection, monitoring, and response planning, so that we won’t be as blindsided by the next Zika-like outbreak.