Dry weather won't prevent West Nile virus
Monday, July 11, 2005
by JIM RITTER Health Reporter
While dry weather has sharply curtailed nasty floodwater mosquitoes, the drought is favoring a less-common mosquito that carries the West Nile virus.
Floodwater mosquitoes, which are vicious biters, breed in standing water, such as birdbaths, backyard ponds, wetlands and lowlands flooded by the Des Plaines and other rivers. With so little rain, their numbers are way down.
"A lot of people are remarking that they've been out in the backyard and haven't seen a mosquito," said Laura McGowan of Roselle-based Clarke Mosquito Control.
Rainfall is 8 inches below normal
Rainfall in the Chicago area has been below normal since February, and the National Weather Service says the region is in "extreme drought."
The drought region stretches from Chicago to west central Illinois and into northeast Missouri.
Since March 1, only 5.8 inches of rain has fallen at O'Hare Airport, 8.6 inches below normal.
This means while floodwater mosquitoes have not been able to thrive, the summer climate has been ideal for the culex mosquito, which thrives in hot, dry weather.
However, scattered showers in late June and on July 4 will trigger mild to moderate outbreaks of floodwater mosquitoes as early as Tuesday in McHenry County, Wednesday in south Cook County and Sunday in south Lake County, Clarke predicts.
No human cases yet this year
This summer has been ideal for the culex mosquito, which breeds in stagnant water and thrives in hot, dry weather. Culex mosquitoes become infected when they feed on infected birds, then spread the infection to other birds and mammals, including people.
Culex mosquitoes are not as irritating as floodwater mosquitoes, and health officials are warning folks not to let their guards down.
"A hot summer, like that of 2002, could increase mosquito activity and the risk of disease from West Nile virus," the Illinois Public Health Department said.
In 2002, Illinois led the nation with 884 human West Nile cases and 66 deaths. The number of infections were down sharply in 2003 and 2004, which had cooler, wetter summers.
About 20 percent of people bitten by an infected mosquito will experience West Nile illness, which usually is mild and includes fever, headache and body aches. However, serious illness, including encephalitis and meningitis, can occur, especially in people older than 50.
Since May 1, about 43 batches of mosquitoes and six birds have tested positive for West Nile virus in 16 counties. The Chicago Public Health Department collected its first positive mosquito sample on July 1 in the Beverly neighborhood. No human cases have been reported in Illinois so far. Such cases usually don't show up until late summer or fall.
To avoid bites, health officials recommend staying inside between dusk and dawn, when mosquitoes are most active. When outside, wear shoes, socks, long pants and a long-sleeved shirt, and apply a repellent that includes DEET, picaridin or oil of lemon eucalyptus.