The increasing number of mosquitoes spreading the Zika virus across Miami-Dade County, Fla., and on Miami Beach is triggering more aggressive control efforts, county officials said Friday.

In recent weeks, about 160 traps posted around the county to monitor for Aedes aegypti mosquitoes, the urban mosquito that carries the virus, are increasingly catching more mosquitoes, said Miami-Dade County division director Gayle Love. That’s prompting mosquito officials to up their campaign to prevent another outbreak of the virus. Last year, the county had the first active transmission zones in the continental U.S.

Wherever traps show high numbers of mosquitoes that carry the Zika virus, inspectors with back-pack foggers will spray. Associated Press/Felipe Dana

With the exception of Miami Beach, Love would not say where numbers are high, only that traps countywide are averaging 16 mosquitoes. Anything above 10 is considered high.

Wherever they find high trap numbers, county officials plan on sending inspectors armed with back-pack foggers that apply a pyrethroid-based adulticide, she said.

They will also spread an organic larvicide if they encounter breeding.

So far this year, Florida health officials have confirmed 29 travel-related Zika cases in Miami-Dade County but no locally acquired infections.

Last year, neighborhoods in Wynwood, Little River and the Beach became the first spots in the nation, along with Puerto Rico, where people began contracting the virus. Federal, state and local officials responded with an aggressive war on the mosquitoes, which increase the risk of infection as their numbers rise.

The U.S. Centers for Disease Control and Prevention found that a combination of aerial spraying with the controversial pesticide naled and an organic larvicide succeeded in driving down mosquito populations. But critics have repeatedly complained that naled, which is banned in Europe and kills bees, butterflies and other pollinators, is too risky and that enough is not known about its potential health effects.

After being criticized last year for doing too little in advance of the season despite repeated warnings, county officials this year continued spreading larvicides throughout the winter and spring to keep the mosquito season under control.

So far this season, the county has sprayed naled twice to control marsh mosquitoes, which do not carry the virus.

Last week, a Miami Beach doctor asked a U.S. district judge to order an emergency injunction to stop the aerial spraying. A status conference on the complaint is scheduled Wednesday.

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