How Zika spreads (and who’s to blame)
As the waters from Hurricane Matthew began to recede, coastal residents from Florida to the Carolinas may have something else to worry about: Zika.
The high winds broke through screen doors and windows, knocked out power and left behind small and large bodies of standing water that could serve as new breeding grounds for mosquitoes. Scientists raised concerns that the Zika virus that has touched down in South Florida is now a greater threat to expand and move up the coast.
“It knocks a lot of stuff down so you just have a lot more things in which the mosquito can breed,” said Philip Stoddard, a Florida International University biology professor and the mayor of South Miami. “A damaged rain gutter, for instance, now becomes a rain collector. Every little object that blows off a house or even a chair flipped over on a porch becomes a container for mosquitoes to breed.”
Most adult mosquitoes won’t survive the gusts of wind, and flooding will wash away young mosquitoes. Those that survive, however, will lay new eggs near standing water that will hatch over and grow over the next week, likely boosting the bug population.
So when you’re out there rebuilding your house, you’re not thinking about the mosquitoes that are biting at your ankles at the time.
Kevin A. Caillouët, St Tammany Parish Mosquito Abatement District
Raising concerns for coastal communities in Florida, Georgia and the Carolinas is that there was a spike in neurological disease cases associated with the West Nile Virus after Hurricane Katrina. In 2006, the cases of West Nile virus more than doubled in the hurricane affected areas of Louisiana and Mississippi, according to a 2008 Centers for Disease Control and Prevention study.
“The immediate increase in cases may be attributed to increased human exposure to mosquitoes,” wrote Kevin A. Caillouët, a Tulane research fellow at the time, in the CDC report. “Tens of thousands of persons in the hurricane-affected region were living in damaged housing or were waiting outside for days to be evacuated.”
In Louisiana, no cases of West Nile virus were reported in the weeks leading up to Hurricane Katrina, but 11 were reported in the following three weeks where the storm hit. A similar pattern was seen in Mississippi, where 10 cases of West Nile were discovered in the three weeks after the storm.
Caillouët, who is now assistant director of the St Tammany Parish Mosquito Abatement District near New Orleans, emphasized West Nile and Zika are two different diseases and earlier studies showed no increase in viruses after storms.
But he said there are common characteristics that should be taken into consideration. Hurricanes cause people to change their daily habits, which can make them vulnerable to bug bites by, for example, opening doors because the air conditioning doesn’t work and spending more time outside fixing what was broken.
“So when you’re out there rebuilding your house, you’re not thinking about the mosquitoes that are biting at your ankles at the time,” Caillouët said. “You’re thinking about getting your house back in order.”
CDC officials said studies show that hurricanes and floods do not typically cause an increase in the spread viruses by mosquitoes, but spokesman Benjamin Haynes acknowledged some could and it’s better to take precautions.
“Small increases in the numbers of [West Nile Virus] cases were noted in some areas of Louisiana after Hurricane Katrina,” Haynes said. “After a hurricane or flood, the health department or mosquito control district will often take steps to reduce the mosquito population. Residents can help control mosquitoes in and around your home and prevent mosquito bites.”
The hurricane was expected to temporarily interrupt mosquito control efforts in Miami as spraying pesticides would not be effective during strong winds.
Gov. Rick Scott asked Florida residents to drain standing water before and after the hurricane.
Every little object that blows off a house or even a chair flipped over on a porch becomes a container for mosquitoes to breed.
Philip Stoddard, a Florida International University
Stoddard said Friday that local officials in South Florida had not had the time to discuss the mosquito issue, but he said the hurricane largely missed South Miami. The greater consideration, he said, is further north.
But Derric Nimmo, principal scientist for Oxitec, which has developed genetically modified mosquitoes that are being considered for release in Key West, said time will tell. It’ll take about a week for transmissions to rise as the mosquito population grows. But he said “risk is risk,” which also means transmissions may not increase.
“But if you pull those factors together, they got Zika, they got active transmissions, they got the mosquito,” he said. “The rain will dump a lot of water. Then the risk should be taken into consideration that it’s going to be relatively high that it might spread.”