U.S. mosquitoes now spreading Zika virus

The infections occurred in Miami, Florida

A virus researcher works with Zika samples at the National Institute of Allergy and Infectious Diseases Vaccine Research Center. 

NIAID/ FLICKR (CC BY 2.0)

Four new cases of Zika infection have turned up in Florida residents who could not have caught the disease during foreign travel. They also were not exposed to others sick with the disease. That suggests they had to pick up the virus while living at home — from local mosquitoes.

Florida’s health department made the unsettling announcement on July 29.  These cases would be the first due to local mosquitoes in the continental United States.

“Zika is now here,” Tom Frieden said at a news briefing the same day. Frieden directs the U.S. Centers for Disease Control and Prevention in Atlanta, Ga.

No trapped mosquitoes have yet tested positive for the virus. Still, health officials suspect that mosquitoes within a small region in north Miami are to blame. “Everything we’ve seen so far indicates that this is mosquito-borne transmission,” Frieden said.

The local mosquitoes include Aedes aegypti (AY-dee E-JIP-tye). This is the same species that has been spreading the virus throughout Latin America. Florida’s small cluster of cases does not mean an epidemic is coming, Frieden said. The four infected people probably were bitten in early July.  Since then, Florida has stepped up efforts to stamp out mosquitoes. People have been going door-to-door to get rid of standing water, where mosquitoes can lay their eggs. Public health teams also have been spraying bug killers.

“We believe that widespread transmission in the continental U.S. is unlikely,” Frieden said. “But it’s not impossible.”

Two other mosquito-borne diseases, dengue and chikungunya, have spread locally in Florida in the past. But, Frieden noted, those diseases generally die out after infecting just one person.

More Stories from Science News for Students on Health & Medicine