West Nile risk rising in northern suburbsTests show increase in infected mosquitoes
Friday, August 18, 2006
by Brian Cox
The number of mosquitoes in the north suburbs testing positive for West Nile virus is on the rise, and there is an increased risk to humans of catching the disease, officials said.
"We have known all along that there's West Nile virus in this community," said Carla Bush, chief of community health services in Evanston. "The only difference now is that there's a better probability that people may get bitten by a mosquito that's infected."
The West Nile virus infection rate among mosquitoes trapped by the North Shore Mosquito Abatement District shot up by about 40 percent last year, and based on mosquito collections so far this year, it appears to be going up again, said Supt. Robert Berry.
As of Monday, 27 percent of mosquito pools the district sampled tested positive for the virus, according to the district's communications director, David Zazra.
Communities in Lake County are also experiencing an increase in mosquitoes testing positive for the virus, said George Balis of the Clarke Mosquito Control Co. in Roselle. He said the company works with the South Lake Mosquito Abatement District in Deerfield, Highland Park, Riverwoods, Highwood and Bannockburn.
In June, about 15 percent of the mosquito samples came back positive for the virus, Balis said. In the first week of August, 47 percent of the samples tested positive, which he said compares with 41 percent during the same period last year and 18.8 percent in 2004.
"People should not be afraid of being outside," Balis said. "It's just a situation where people need to take precautions."
Berry said there is a greater risk of humans contracting West Nile virus whenever 10 percent or more of the mosquitoes collected test positive for the disease. He said this summer's dry, hot weather makes for ideal mosquito-breeding conditions.
"More research needs to be done at the end of the season," he said "The season ends with the first frost."
So far this summer, the North Shore Mosquito Abatement District has collected about 25 dead birds that had the virus across its area, which runs from Lincolnwood north to the Cook County line.
Cook County officials are also receiving calls from people who have found dead birds, Berry said. The Illinois Department of Public Health confirmed earlier this week that a dead crow found in Evanston tested positive for the virus, Bush said.
Berry said workers sprayed pesticide at various locations in Glencoe on Tuesday night and in Lincolnwood on Wednesday night. He said they are also spraying in other north suburbs.
"That involves firetrucks equipped with low-volume sprayers that put out a light mist," Berry said. "It's a quick kill for mosquitoes that are flying at that time."
Pesticide spraying in the North Shore district started in Skokie in mid-July after mosquitoes testing positive for the virus were found in traps in the village, Berry said.
As of Wednesday, three people in suburban Cook County had been diagnosed with the virus, but that number is likely to climb as more people start developing symptoms, said Kitty Loewy, spokeswoman for the Cook County Department of Public Health.
"Those three cases are all from the south suburbs, but that doesn't mean there aren't problems elsewhere," Loewy said. "The number of reported cases goes up in August, following peak mosquito season."
Six cases have been diagnosed in the state so far this season, according to the Illinois Department of Public Health.
Mosquitoes become infected with West Nile virus after biting an infected bird and can spread the virus to the humans they bite, Berry said. Most people with the virus will not become ill, but some will begin to show flulike symptoms 3 to 14 days after being bitten. While most people recover from the illness, some have long-term health effects, and a small number die.
Bush said her office is advising residents to reduce their risk of mosquito bites by limiting time spent outdoors during peak mosquito-biting hours, which are between dusk and dawn.
She said other precautions include keeping lawns cut short; wearing pants, socks and shoes and long-sleeve shirts when outdoors; using a repellent containing DEET, picaridin or oil of lemon eucalyptus; repairing screens on doors and windows; and eliminating standing water where mosquitoes breed.
Berry said mosquitoes prefer to breed in the 60,000 catch basins in the North Shore district.
Mosquito abatement starts in April when pesticide ingots are dropped into catch basins and continues through the summer with spraying, trapping and testing, Berry said.
"We're mosquito abatement, we're not mosquito eradication," he said. "We suppress the mosquitoes the best we can with the tools available to us."