This weekend saw the first local transmission of the Zika virus in the continental United States. As of Wednesday, 15 people in Florida have contracted the disease from infected mosquitoes. While officials don’t anticipate additional cases of “homegrown Zika,” the amount that the virus has spread thus far may be due to longer mosquito seasons caused by climate change.
Since being discovered in Uganda in 1947, Zika has remained rare. In 2014, however, the disease erupted in Brazil and has since spread across South America and the Caribbean, infecting hundreds of thousands of people. More than 4,600 Puerto Ricans alone have contracted Zika from mosquitoes.
The virus can be transmitted through sex or by mosquitoes. Mosquitoes that transmit Zika, principally the yellow fever mosquito (Aedes aegypti), thrive in warm climates, leading some to speculate that global warming has fueled the spread of the illness.
A new project from Climate Central shows that rising temperatures and increased humidity have lengthened mosquito season. The number of days with the ideal conditions has risen most dramatically in the Midwest and on the East Coast. In Baltimore, Maryland and Durham, North Carolina, the mosquito seasons have been extended by almost 40 days in the last 35 years.
Among major U.S. cities, Miami boasts the longest mosquito season: 337 days. The city offers extremely favorable conditions to Asian Tiger Mosquito (Aedes albopictus), another carrier of the Zika virus.
Officials don’t believe that Zika will become widespread in the United States, but the extended mosquito seasons are still a cause for concern — especially as U.S. lawmakers have yet to agree on a Zika funding package to help fight the virus. Other mosquito-borne diseases, like Dengue fever, are also still a serious issue in other parts of the world.
Most people who are infected with Zika experience no symptoms. Roughly 20 percent only develop mild symptoms, like a fever, rash, nausea, or joint pain. Still, Zika is pernicious for expectant mothers. Fetuses infected with the disease may develop abnormally small heads, leading to mental disability and early death.
Officials are encouraging people in mosquito-prone areas like South Florida to wear insect repellent and cover up. The Centers for Disease Control and Prevention has discouraged pregnant women from traveling to high-risk areas, including northern Miami and Puerto Rico.