Hurricane Matthew: Potentially Bad News For Fight Against Zika Mosquitoes

Oct 5, 2016

Hurricanes can create new breeding sites for mosquito larvae.
Credit nature.mdc.mo.gov

Mosquito control and health officials are hoping mosquito prevention is on the minds of Floridians preparing for Hurricane Matthew.

Hurricanes can create perfect conditions for an explosion in mosquito populations.

“Generally what we’ll see post-hurricane is that mosquito populations will go down for the first week or two,” says Steve Bennett, a professor of global health at the University of St. Thomas in St. Paul. “Mainly because it washes away many of the eggs that have been laid—and hurricanes can also kill or blow away a lot of the adult mosquitoes.”

The real mosquito problem, Bennett says, comes next.

“After that point, we then see them boom,” he says.

Debris and destruction from a storm can create new mosquito breeding sites, pooled with water from all that rain. People then go outside during the recovery period, providing ample opportunity for mosquitoes to feed—which is also an opportunity to spread viruses like Zika and Dengue.

This is a good moment to realize that there may be places on your property that can hold standing water.

Potentially making it worse: Miami-Dade County Mayor Carlos Gimenez said at a press conference this week that storm conditions could interrupt mosquito control.

“Those efforts will stop once we get to tropical-storm-force winds and hurricane-force winds,” said Gimenez.

In preparation for Hurricane Matthew, the county has temporarily taken down mosquito surveillance traps so that they don’t blow away. The plan is to put them back up when conditions are safe.

Benjamin Haynes, a spokesperson with the U.S. Centers for Disease Control and Prevention, wrote in a statement:

Typically, we associate severe rain events such as tropical storms and hurricanes with increases in nuisance mosquitoes rather than the mosquitoes that transmit Zika virus. This is because the mosquitoes that transmit [Zika virus] develop in small containers in and around homes that are disrupted by heavy rains and flooding.  Additionally, populations of adult mosquitoes, including those that are alive and currently infected, are likely to be disrupted by heavy rains.

These observations suggest that in the short term heavy storms can actually have a beneficial effect on the risk of transmission. Looking forward to the coming weeks, it is difficult to know what effect this storm will have on the risk of local, mosquito-borne Zika transmission in Florida. Consequently, CDC will continue to work closely with the Florida DOH to monitor the situation in Florida, identifying human cases and controlling local populations of mosquito vectors.

In the meantime, it is important for people to protect themselves from mosquito bites.  We encourage everyone to use insect repellent when you go outdoors, wear long sleeves and pants.  Use air conditioning if possible.  Empty standing water from items outside your home, such as gutters, kiddie pools and birdbaths.

Gayle Love with the Miami-Dade County Department of Solid Waste Management—which also oversees mosquito control for the county—says the message is basically the same for hurricanes and Zika prevention.

“Drain any standing water and then cover yourself. Cover your windows and doors and cover yourself with repellent,” says Love. She points out that securing the sorts of things that could become mosquito breeders is also a way of preventing them from becoming flying debris in high winds.   

Love says after a storm the emergency response plan starts with clearing roadways and public spaces. Individuals are encouraged to do what they can to control mosquitoes on their own properties.

“This is a good moment to realize that there may be places on your property that can hold standing water,” says Matthew DeGennaro, a mosquito researcher with Florida International University.

DeGennaro says the greater Matthew-related mosquito danger will likely be to places like Haiti where the destruction of manmade structures is particularly severe and widespread.

“In Haiti, they may be facing all sorts of problems afterwards,” he says, adding that the country already has a hard time with mosquito-borne illnesses, like malaria, that are not found in Florida. “I think they might see a spike in vector-borne illness, even more acutely than we will.”

And while hurricanes have been associated with spikes in mosquito-borne diseases in other places, Steve Bennett says it’s not time to freak out in Florida just yet.

“One good thing to keep in mind is that these kind of massive weather effects have never caused an outbreak of mosquito-born disease in the United States,” says Bennett.

Still, he says, the state’s Zika problem—and the virus’ unusual ability to be passed by mosquito or sexual contact—makes this an unprecedented situation.