While mosquito populations tend to surge following flooding or other natural disasters like a tropical storm, there is rarely a threat to public health as infected-mosquito populations are usually destroyed in the wake of the event.
"Surveillance is routinely conducted to assess what mosquito species are found post flood," CDC National Center for Emerging and Zoonotic Infectious Diseases Press Officer Candice Burns Hoffmann said.
Weather can directly impact how mosquito populations increase and lead to greater risks of disease like the Zika virus, which has become a growing concern as cases of local transmission spread across much of South and Central America.
"Most commonly, nuisance mosquito populations, not disease-causing mosquitoes, surge post flood event, and these mosquitoes can quickly impede flood recovery efforts," Hoffmann added. "People don't like getting bitten."
In a paper published by Roger S. Nasci and Chester G. Moore of the Centers for Disease Control and Prevention, research has shown that epidemics of mosquito-transmitted disease rarely follows natural disasters in the United States. In addition, high winds also will kill adult mosquitoes, which are weak fliers.
"Nevertheless, public health disaster response policies should include a provision for monitoring increases in the prevalence of potentially infectious mosquitoes and the risk for arboviral disease in the affected areas," Nasci and Moore report.
"In 1975, there was one instance where cases of Western equine encephalitis increased after a flooding event," Hoffmann said, citing the Nasci-Moore paper.
"However, it's important to understand that flooding alone doesn't increase the risk of virus transmission. The virus has to be found in the environment, or in a person, bird, or animal, for mosquitoes to become infected and infect others," she added.
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In the case of West Nile virus and the mosquitoes that transmit it, drought is another type of natural risk factor.
"The Culex pipiens and Culex quinquefasciatus mosquito species that transmit [West Nile Virus] to people prefer hot and dry conditions," Hoffmann said.
"They breed in stagnant water with high organic content [such as] ponds, ditches, and abandoned swimming pools. In hot weather, the life cycle is much shorter so mosquito populations increase in these conditions."
Following the incidence of flooding or a natural disaster, the CDC conducts surveillance and are more concerned with the surge in nuisance mosquito populations in the wake of a severe weather event.
"Despite the fact that epidemics of arboviral encephalitis have rarely followed hurricane, or flood-related disasters in the United States, these events can increase the risk for human arboviral disease in certain circumstances," Nasci and Moore's report warns, citing that in nine of the ten events in which surveillance was conducted, arbovirus activity was detected after surveillance began, indicating a transmission cycle in the area.