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CDC: Aerial spraying likely helped stop Zika spread in Miami
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The CDC says aggressive aerial spraying likely halted the local spread of Zika virus in Miami by rapidly reducing the population of mosquitoes that spread the disease.
After ground efforts such as spraying from trucks and backpacks failed to effectively control the population of Aedes aegypti in the affected Wynwood neighborhood, a combination of low-volume spraying with insecticide and larvicide led to what CDC Director Thomas R. Frieden, MD, MPH, called a “rapid knockdown” of the mosquito population.
Frieden spoke during a teleconference today detailing a new report by the CDC on Florida’s response to the first local Zika infections in the United States. He said Zika transmission from mosquitoes to people appears to have stopped in early August in Miami, about the same time that aerial spraying began.
“At this point, aerial application appears to be our strongest tool, so new tools will have to be assessed against that,” Frieden said. “This heralds a new era for standard of control of local transmission.”
The aerial response involved spraying the controversial insecticide naled, which is used to kill adult mosquitoes, across 10 square miles. That was followed by alternating applications of naled and the larvicide Bacillus thuringiensis israelensis in a centralized area of 2 square miles.
The results led the CDC on Monday to relax its travel guidance for the Wynwood neighborhood after 45 days with no evidence of active Zika transmission, including lifting its warning that pregnant women not visit the area.
The outbreak in the neighborhood just north of downtown Miami occurred between June 30 and Aug. 5. According to the CDC report, officials were first tipped off that local transmission might be occurring in Wynwood when the only connection between two of the first four patients was that they worked within approximately 130 yards of each other.
At the same time that the CDC lifted its travel warning for Wynwood, officials expanded the area in Miami Beach where infected mosquitoes are believed to still be biting people. It now reaches from 8th Street to 63rd Street, an area of 4.5 square miles.
Florida is still the only state in the U.S. where mosquitoes infected with Zika are known to be biting people. The state has reported nearly 100 such locally transmitted cases since late July from Miami and Miami Beach.
Celeste Philip, MD, MPH, surgeon general and secretary of Florida, said during the teleconference that initial data suggest aerial spraying also has been effective at lowering the mosquito population in Miami Beach, although the area’s geography and tall buildings make it harder to spray. Because of safety concerns, planes are being used to spray instead of helicopters, which can traditionally spray lower to the ground, she said.
According to the CDC, aerial spraying in Wynwood did not lead to an increase in ED visits by patients experiencing related illnesses such as asthma, reactive airway disease, wheezing, shortness of breath, nausea, vomiting or diarrhea.
Still, the safety of naled has been debated, but the FDA considers it safe when used properly, Frieden said. The insecticide has been registered since 1959 for use in the U.S. but is not registered for use in Europe and has been rejected by officials in Puerto Rico despite that country’s epidemic of local Zika transmission.
Frieden said concerns about the insecticide’s impact on humans and the environment was understandable, but outweighed by the effects of Zika.
“We wish insecticides never had to be used,” Frieden said. “We wish Zika were not causing birth defects also.” – by Gerard Gallagher
Reference:
Likos A, et al. MMWR Morb Mortal Wkly Rep. 2016;doi:10.15585/mmwr.mm6538e1.
Disclosures: Frieden is the director of the CDC. Philip is the surgeon general and secretary of Florida.