NPR reports that the mosquito-borne illness is probably here to stay:
So far, local officials in Miami have successfully cleared just one zone of local Zika transmission — the Wynwood neighborhood. In Miami Beach, despite intensive mosquito control efforts, including aerial spraying with the chemical insecticide Naled, new Zika cases forced health authorities to triple the size of the zone.
This month, after weeks of treatment, a trap showed new mosquitoes still carrying the virus.
That’s led activists and some scientists to question the effectiveness of the aerial spraying. [Miami-Dade Mayor Carlos] Gimenez says Naled worked, when used in combination with Bacillus thuringiensis israelensis, or Bti — a naturally occurring soil bacterium that can be deployed to kill the mosquito larvae that tend to linger in puddles of standing water.
“We saw mosquito counts drop dramatically in the south sector where we did it,” Gimenez says. “We saw mosquito counts drop and remain low in Wynwood. So, it’s definitely effective.”
What makes Zika so hard to control is the mosquito that carries it. After many centuries of living in close proximity to people, Aedes aegypti mosquitoes have adapted. They hide in closets and under tables and in foliage — places where spraying often doesn’t reach. Especially in an area with high-rise buildings, like Miami Beach, aerial spraying is not considered effective for A. aegypti.
Philip Stoddard is the mayor of South Miami. But he’s also a biologist at Florida International University. He used the county’s data to do a statistical analysis of the aerial Naled spraying, and found it had “very little measurable and statistically significant effect” on Miami Beach’s mosquito population, he says.
The analysis shows that aerial spraying was more effective in Wynwood, Stoddard says, a neighborhood without high-rises. In both places though, it was use of the bacterial larvicide, he says, that produced the long-term declines in mosquito population.
“Unfortunately,” [tropical disease specialist Dr. Michael] Callahan says, “in all of our Zika mosquito control efforts in southeast Asia, West Africa and here in the tropical Americas, once the virus has entered the local Aedes mosquito populations, we’ve never been able to get it out — totally out.”
Florida tourism officials have yet to issue their statement….