Two years after the first Zika outbreak in the continental United States landed in South Florida, Miami-Dade County officials said Wednesday they're in full-blown battle mode as this month's heavy rain kicks mosquito season into high gear.
"It’s our responsibility, all of our responsibility," Mayor Carlos Gimenez said in a press conference urging residents to begin paying more attention to standing water where urban, disease-carrying mosquitoes breed.
"If we don’t get bit, we won’t get a disease and if we don’t have a disease, we won't transmit the disease," he said. "Fight the bite."
Since the summer of 2016, when Florida had more than 1,400 confirmed Zika cases, the county has substantially beefed up a mosquito-fighting division overwhelmed by an outbreak that led to active transmission zones in Miami Beach and Wynwood. A zoologist with a doctorate in mosquito biology was named director last year and the number of inspectors nearly tripled to 38. The county also began putting together its own fleet of sprayers, treating Wynwood and Miami Beach year round, and increasing the number of surveillance traps to monitor populations to 186 around the county.
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Last mosquito season, the county nearly escaped without a single locally contracted case: the first wasn't detected until November.
So far this year, the number of Aedes aegypti mosquitos that carry diseases have been relatively normal, Deputy Mayor Alina Hudak said. None have tested positive for Zika or any other diseases, she said. However, that could change with heavy rain forecast for the week ahead.
"Obviously we’re watching that very carefully," she said.
The county's efforts to combat Zika may also help with a new threat: yellow fever. Beginning in early 2018, a large number of cases began appearing in Brazil, where the Zika epidemic originated, with more than 300 deaths so far, according to Lillian Rivera, county director for the Florida Department of Health. County officials now fear travelers may spread yellow fever to the U.S., which hasn't had an outbreak since 1905. Unlike Zika, yellow fever has a vaccine but most people don't initially realize they've been infected.
"Definitely it's an astounding amount of cases that we need to be concerned about," she said.
Over the coming months, Mosquito Control Director Bill Petrie said the county will continue larviciding in the two former transmission zones and treating areas where traps show counts over 10. An ongoing project in South Miami to control populations with lab-bred male mosquitoes infected with a bacteria that stops reproduction is also showing early signs of promise, he said. But more work needs to be done. Naled, an aerial pesticide banned in Europe and lethal to bees and butterflies, may also be used, but as a last resort.
Larviciding with an organic pesticide called BTI remains the weapon of choice, he said.
"Guys in the field like it because it’s quick killing. It’s very effective. It’s very efficient. They know if they go back three hours later they’ve got a result. And it's nontoxic to humans, mammals, birds, fish," he said. "It’s a godsend for people in my business."
An earlier version of this story incorrectly stated the number of county inspectors hired since 2016 and trap counts that trigger larviciding.