Scientists say a “perfect storm” of events has triggered the terrifying epidemic.
—By Tim McDonnell
| Thu Jan. 28, 2016 6:00 AM EST
A worker in Brazil disinfects the famous Sambadrome as part of the fight against the mosquito Aedes aegypti, which spreads the Zika, dengue, and chikungunya viruses. Marcelo Sayao/ZUMA
The outbreak of Zika virus in Latin America is “spreading explosively,” the director of the World Health Organization warned at an emergency meeting in Geneva on Thursday. Last week, the epidemic took a surreal turn when health officials in El Salvador advised women there not to get pregnant for the next two years. Similar, though less extreme, warnings have been issued by Brazil, Colombia, and several other countries. The virus has infected more than 1 million people during the current epidemic, and health officials say it may be linked to a spike in microcephaly, a rare condition in which infants are born with unusually small heads.
Behind the outbreak is a complex combination of environmental and economic factors. Here’s what you need to know:
What is Zika? Zika was first identified in monkeys in Uganda’s Zika Forest in 1947. In the years since, the disease has slowly migrated eastward around the globe, following oceanic trade routes with the help of infected sailors and mosquitoes trapped in the holds of ships. The first serious outbreak occurred in 2007 in Micronesia, where up to 60 people were infected, followed by cases in French Polynesia and on other Pacific islands. The current outbreak, which started late last year in Brazil, is the most serious yet and the first one in the Americas.Zika is carried by Aedes aegypti, the same species of mosquito that carries dengue fever, yellow fever, and chikungunya. Compared with those other viruses, the symptoms of Zika are very mild, most often resembling a bad cold or the flu. Deaths from the virus are rare. People can contract the virus if they are bitten by a mosquito that has previously drawn blood from another infected person; apart from mother-to-fetus transfer, there’s no evidence yet of person-to-person transfer. There is no vaccine or treatment.
Why is Zika a concern for pregnant women? In pregnant women, the virus could be the cause of a rapid uptick in cases of microcephaly, which causes incomplete brain development. In Brazil, cases of microcephaly rose 30-fold between 2014 and 2015, from 147 to nearly 4,000 cases, just as the Zika outbreak was taking place. That apparent correlation led to the precautionary pregnancy advisories, but scientists have yet to definitively confirm their suspicion that Zika is directly to blame for microcephaly.
What’s the cause of the outbreak? According to Laurie Garrett, senior fellow for global health at the Council on Foreign Relations, the outbreak was triggered by “a perfect storm” of biological, economic, and climatic events. Aedes aegypti, the mosquito that can carry Zika, has been growing in population in Latin America since first being introduced to Brazil via trans-Pacific shipping routes in the late 1980s. Brazil is also now in the middle of a severe economic downturn, while the government is in disarray as President Dilma Rousseff faces calls for impeachment for her involvement in a corruption scandal involving Petrobras, the state oil company. That has left the country with a weakened public health system that is struggling to effectively eradicate dangerous mosquitoes. This week, Brazil’s health minister admitted he was “badly losing the battle” against mosquito-borne illnesses.
But the most important factor, Garrett said, is a mosquito population boom triggered by above-average rainfall, a product of this year’s exceptionally strong El Niño in the Pacific. Over the last month, flooding in Brazil, Paraguay, and elsewhere has been the worst in half a century, forcing 150,000 people to evacuate their homes. Those conditions are perfect for mosquito breeding.
“One of the hallmarks of these mosquitoes is they like very clean water,” Garrett said. “So rainfall is perfect for them. If it creates puddles, or accumulates in tires or any sort of containers, that will be a breeding site.”
Combine that with steamy summer temperatures and lots of bare skin, and it’s easy for a mosquito-borne disease to spread quickly. Along with the Zika outbreak, Garret said, dengue is also surging.
What about climate change? For environmentalist Bill McKibben, government warnings against getting pregnant were a shocking preview of the climate change dystopia just around the corner.
“Think about that. Women should avoid the most essential and beautiful of human tasks. It is unthinkable,” he wrote in an op-ed for the Guardian on Monday. “Obviously we need to face up to the fact that pushing the limits of the planet’s ecology has become dangerous in novel ways.”