Published on 06/16/04

Expected summer West Nile Virus cases a low show

By Faith Peppers
University of Georgia

Many public health watchers predicted this to be a very active year nationwide for West Nile Virus and other mosquito-borne illnesses. But so far, all's quiet on the Southern front.

"As for WNV, things have been pretty quiet up to this point," said Elmer Gray, a University of Georgia Extension entomologist and a member of the Georgia West Nile Virus Task Force. "The common thought is that we will have a similar case load as last year (55 cases and 4 deaths)."

Many thought the area would continue to see eastern equine encephalitis activity throughout the season, but dry weather may have squelched this activity, Gray said. "The vectors for EEE are swamp mosquitoes (Culiseta melanura), and I suspect that the swamps have less water than normal," he said.

His suspicions are confirmed.

Dry weather a plus

"The Suwanee River coming out of the Okeefenokee Swamp has set daily low-record flows for this time of year," said State Climatologist David Stooksbury. "I'm not sure what that does to the mosquito population, but [the river] is low."

Most would think that wet weather leads to more mosquitoes. If standing water is left around homes following rain, that's true. However, it's dry weather that brings the boom of mosquitoes to urban areas.

"The [WNV-carrying mosquitoes] breed in storm drains of downtown city areas," Gray said. "When it rains, it actually flushes out the drains. Cases of WNV or St. Louis encephalitis actually come on after a dry spell when water has been laying [stagnant], giving mosquitoes a chance to breed."

Weather could aid in the fight against mosquito-borne illnesses this year.

"The early part of this summer, rainfall has been less and therefore less standing water is around to serve as a breeding ground for mosquitoes," Stooksbury added.

Plan working?

That could lessen mosquito numbers, but Gray has another theory. The state has made great strides in improving its ability to conduct surveillance for all mosquito-borne diseases. And the public health field, in general, is much better prepared and able to detect mosquito-borne viral activity of any type.

With this in mind, Gray notes there has been very little WNV activity detected and dead bird submissions are behind previous years.

"We in the mosquito field would like to think that our larval suppression programs have contributed to the lessening of WNV activity," he said, "but that is very difficult to measure. Particularly since no one wants to be the control (untreated) group that would be necessary for a legitimate study."

Use caution

Even though the state is seeing low numbers of mosquito-borne illnesses, it's still important to use the proper precautions.

"As always, it is important that people remember to try to avoid peak periods of mosquito activity (dawn and dusk), eliminate standing water around homes and wear insect repellents containing DEET when in areas with mosquito activity," Gray cautioned. "It's quiet now, but it's still early. Things could change later in the summer."

For more information on West Nile Virus and how to avoid it, visit the UGA College of Agricultural and Environmental Sciences WNV Web site.

Faith Peppers is the director of public affairs with the University of Georgia College of Agricultural and Environmental Sciences.