MIAMI — 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 infection from a mosquito bite on the U.S. mainland 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.