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3 pregnant women have tested positive for Zika in Florida. Here's how the state is preparing for an outbreak.

In Florida, three pregnant women have tested positive for the Zika virus — the mosquito-borne disease that's currently raging across Central and South America.

All of the women were infected while traveling abroad, the Miami Herald reports.

The news is concerning for two reasons: 1) Zika virus has been linked to birth defects. It's possible the babies of these women are at risk for microcephaly, a condition where a baby is born with a smaller-than-average head. 2) The more cases that arrive in Florida, the more likely it becomes Zika virus will establish a presence in the state.

Florida may see some small outbreaks of Zika Virus

Florida Gov. Rick Scott declared a state of emergency over Zika at the beginning of the month. The order originally covered four counties where Zika patients lived, but has since expanded to cover 11.

The main worry isn't that these travelers brought over live mosquitoes carrying the disease. It's that Florida's native mosquitoes may bite someone who is infected, suck the virus up into their bodies, and then spread it to other people.

"Then other mosquitoes become infected from feeding off of those people," Walter Tabachnick, a former director of the Florida Medical Entomology Lab, says. "You can see how explosive, how efficient, this mosquito is at doing this. Just look at the number of cases." In Central and South America, the World Health Organization estimates the virus has infected 3 million to 4 million people.

Across Florida, the virus has infected at at least 32 individuals. A month ago, there were just 12 infections (all the cases originated abroad). Because Florida has populations of the type of mosquito (Aedes aegypti) that carry the virus, it's been pegged as a potential hot spot for the disease.

Because Zika is new to the United States — meaning people have no natural immunity to it — there is some fear that the virus could cause a few outbreaks. The state has seen outbreaks of mosquito-borne diseases before. And it knows how to deal with them.

South Florida, a seen from Space. NASA

South Florida, as seen from space. (NASA)

Zika is likely to infect some local mosquitoes. We know this because similar foreign diseases have done this before.

Florida is an ideal target for the Zika virus for a few reasons:

  • It has a warm, tropical climate where mosquitoes can breed year-round.
  • It's also already home to the two mosquito species known to transmit Zika: Aedes aegypti and Aedes albopictus. (The bigger concern is the Aedes aegypti variety, which has a particular fondness for biting humans.)
  • Many travelers to and from Latin America pass through Florida every day.
  • And we know the Aedes aegypti mosquitoes there have, in recent years, infected people with viruses thought to be inactive in the United States.

Dengue fever — sometimes called "breakbone" fever for its intensity — was eradicated from the United States in the 1940s. In the decades since, most of the cases in Florida were travel-related. But in 2009, an outbreak in Key West showed that the virus had again begun circulating among local mosquitoes. Between 2009 and 2010, there were 88 cases of dengue in the Keys, according to the Florida Department of Public Health.

In 2013, dengue took hold in Martin County, on Florida's Atlantic coast. Twenty-eight people were infected there.

Map of Florida showing counties with reported locally transmitted dengue cases, 2009–2013.
Virology Reports

Similarly, Florida has also seen several small outbreaks of chikungunya fever, another viral disease spread by the Aedes mosquito, in recent years. Like Zika, dengue and cikungunya are rarely fatal, but there is also no vaccine to stop their spread.

How can Florida respond to a local outbreak?

In general, mosquito-borne diseases aren't as big a worry in the United States as they are in poorer tropical countries. Screened-in windows and air conditioning units are common here, and they keep mosquitoes out of our homes. So the hope is that any outbreak of Zika in Florida will follow the same path as the dengue and chikungunya outbreaks: They'll be small and localized.

After it became apparent that dengue was spreading in Martin County in 2013, the local mosquito control agency sprung into action. In response, it:

  • Deployed ground-level insecticide sprayers to kill adult mosquitoes
  • Visited homes and businesses, looking for areas where the mosquitoes could breed, and then destroyed those habitats
  • Urged residents to keep their properties clear of mosquito breeding areas
  • Urged everyone to take precautions like wearing bug repellent

According to the Florida Department of Health, "Mosquito control efforts were kept at high levels throughout the outbreak," and in one month they were able to wipe out mosquito breeding in the affected downtown areas.

Tabachnick, who researches the genetic factors that allow mosquitoes to transmit viruses, says it's unlikely Zika will be any more difficult to contain than dengue or chikungunya.

"The betting money is that [Zika] will behave similar to dengue and chikungunya," Tabachnick says. "But we’re going to test that hypothesis when the real thing happens."

Gov. Scott's declaration of an "emergency" sounds severe, but it's really a call for preventive action and increased surveillance.

The declaration will make it easier for the state health department to mobilize and coordinate resources among the county hospitals, the local mosquito control districts, and the national Centers for Disease Control and Prevention.

At the beginning of February, the state requested the CDC send 1,000 kits to test for the Zika virus, and the governor has ordered the state's health department to purchase an additional 4,000. (After the news broke about the infected pregnant women, Gov. Scott requested the CDC send an additional 250 kits, according to the Miami Herald.)

Surveillance will be key. Once authorities can confirm a locally transmitted case of Zika, local mosquito control districts (there are 61
throughout the state) can jump into action. Already, in Miami-Dade and Broward counties — both covered under the emergency declaration — proactive insecticide spraying is underway.

The best response may be just being a good neighbor

The Aedes mosquitoes tend to reproduce in very small pools of water close to a home: in flowerpots, trash, storm drains, etc. Aerial insecticide spraying can't reach into those crevices. Mosquito control has to occur on the ground levels.

That's why homeowners have to be vigilant. And they have to urge their neighbors to be vigilant too.

"You could clean up your house, but if your neighbor has a junkyard producing Aedes aegypti, those mosquitoes are coming to you," Tabachnick says.

Correction: This post originally misspelled Miami-Dade county.

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