A member of the Salt Lake City Mosquito Abatement District handles a fish that eats mosquito larvae on Wednesday, July 20, 2016, in Salt Lake City. The fish will be placed ponds and other standing water in places like abandoned pools. Mosquito abatement teams in Salt Lake City are stepping up efforts to trap and test mosquitoes and kill larvae following the discovery of a unique Zika case that has health investigators trying to figure how the man got the virus. (AP Photo/Rick Bowmer)
A member of the Salt Lake City Mosquito Abatement District handles a fish that eats mosquito larvae on Wednesday, July 20, 2016, in Salt Lake City. The fish will be placed ponds and other standing water in places like abandoned pools. Mosquito abatement teams in Salt Lake City are stepping up efforts to trap and test mosquitoes and kill larvae following the discovery of a unique Zika case that has health investigators trying to figure how the man got the virus. (AP Photo/Rick Bowmer) Credit: Rick Bowmer

Florida mosquito control officials worry they won’t be able to keep up their efforts to contain the bugs that carry Zika without federal funding, even as concern mounts that the first mosquito-borne case in the U.S. is near.

On Thursday, fogging trucks drove through a Miami-Dade County neighborhood where health officials are investigating a Zika diagnosis that doesn’t appear to have connection to travel outside the United States. Zika is usually spread by mosquitoes, but nearly all the Zika cases in the U.S. have been contracted in other countries or through sex with someone who got it abroad.

“We want to make sure we reduce the mosquito population down to zero if possible in this case,” said Chalmers Vasquez, Miami-Dade County’s mosquito control operations manager.

Vasquez’s inspectors are going door-to-door, trapping mosquitoes for testing, hand-spraying and removing the standing water where they breed. Such aggressive mosquito control and surveillance is now routine in Miami-Dade County, which leads Florida in confirmed Zika cases linked to travel.

The Florida Department of Health announced Thursday that another Zika case potentially not related to travel was being investigated in Broward County.

While Zika’s appearance in mosquitoes in the U.S. mainland is likely, health officials don’t expect widespread outbreaks like those seen in Latin America and the Caribbean.

Zika is such a mild disease for most people that they don’t even know they have it, but it has been found to lead to severe birth defects if a pregnant woman is infected.