Wednesday, September 7, 2011

West Nile virus up in Atlanta mosquitoes

The West Nile virus rate in mosquitoes is way up in metro Atlanta this summer compared to last year, and health officials are warning residents to take precautions.

“The hot temperatures and relatively dry conditions probably contributed to the spike in infected mosquitoes,” says Rebecca Levine, a graduate student in Emory’s department of environmental studies. “This may be due to the fact that the heat allows the mosquitoes to develop faster and the lack of rain prevents developing larvae from being flushed out of the system, so they are more likely to
survive to adulthood.”

During Dekalb County’s entire 2010 May-to-October mosquito surveillance, 26 samples of mosquitoes tested positive for WNV, according to the Dekalb Board of Health. This year, with a month-and-a-half remaining for surveillance, the county already reports nearly 80 positive test results. “That’s a remarkable increase,” Levine says.

The peak season for WNV begins in August and continues until the weather gets cooler. Last week, Dekalb County reported the first human case of WNV this year, in a 79-year-old resident of Tucker.

Protect your peeps: Environmental studies students are doing the painstaking work of mist-netting birds and testing them for WNV, to track how the virus moves through an urban environment. Photos by Ryan Huang, above, and Rebecca Levine, below.

To reduce your risk, Levine advises wearing long sleeves and pants and using insect repellant if you are outdoors from dusk through dawn, when the species of mosquitoes that carry WNV are active. For more information about WNV and how to prevent it, call the Dekalb Board of Health, 404-508-7900, or visit its Web site.

The current soaking of metro Atlanta by the remnants of Hurricane Lee may dampen down the mosquito activity a bit, “but they’ll be back, for sure,” Levine says.

Emory’s department of environmental studies is studying the transmission risk of WNV in metro Atlanta. Mosquitoes are the vectors for WNV and birds are the amplifying hosts.

For her dissertation, Levine is monitoring how WNV moves among mosquitoes and birds in an urban environment. At nine different parks and forested areas in metro Atlanta, Emory researchers are capturing birds in mist nets, then tagging them and taking blood samples before releasing them.

“Our preliminary results are showing that the sites where humans are most active have significantly higher transmission rates in birds than in undisturbed urban forests and more secluded portions of parks,” Levine says.

Mosquito monitoring saves lives and money
Sewage raises West Nile virus risk

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