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How do natural disasters affect the spread of mosquito-borne diseases like Zika virus?

By by Michael Kuhne, Staff Writer
May 11, 2016, 10:03:05 AM EDT

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," Centers for Disease Control and Prevention (CDC) National Center for Emerging and Zoonotic Infectious Diseases Press Officer Candice Burns Hoffmann said.

Weather can directly influence mosquito populations and the risk 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.

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"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 CDC, 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.

"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 will conduct surveillance and are more concerned with the surge in nuisance mosquito populations in the wake of a severe weather event.

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