The Zika-Transmitting Mosquito Isn't Only in the Southern US

Does the Aedes aegypti mosquito thrive in tropical and subtropical regions? Yes. But as one study found, the Zika-carrying species can continuously survive in colder parts of the United States.

Mosquito biologist Andrew Lima made the discovery after his friend’s apartment in Washington, DC became infested in 2012, as described on CNN. The friend asked for Lima’s help, but when he got there, he didn’t find the Asian tiger mosquitoes (Aedes albopictus) that are common to the region. Instead, the Capitol Hill apartment was filled with the type that transmits the Zika virus.

What gave it away? Lima saw the mosquitoes had violin-shaped stripes instead of a white stripe down the back. The Aedes aegypti species is also responsible for spreading the dengue and chikungunya viruses. As he investigated further, Lima found more mosquitoes in various locations, including a birdbath and garbage can about a block away from the apartment.

Surely this was a one-time deal, right? Winter would come, the mosquitoes would die, and that would be the end of it… right? But, it didn’t end in 2012 — Lima continued to find the species every time he returned to the area over the next three years.

“I thought, ‘This can’t be right,’” Lima told CNN. He recruited mosquito genetics specialist David Severson from the University of Notre Dame. It turns out that the mosquitoes shared the same genes from year-to-year, which means that they were surviving the winter and breeding.

The team of two hypothesized that the bugs went to underground areas during the colder months. The findings went on to be published in The American Journal of Tropical Medicine and Hygiene.

“Population persistence in the continental United States is reportedly limited to southward of the average 10°C winter isotherm, which in the east, bisects Alabama, Mississippi, Georgia, and South Carolina,” the authors confirmed — up until this recent Washington, DC discovery, of course.

So what does this mean moving forward? Well, there’s still a lot of unanswered questions about the Zika virus. But at least we now know that maybe it’s not about where we know the Aedes aegypti mosquitoes live — but the places we don’t.