CHICAGO -- One year after West Nile Virus began its surge in Illinois, health officials say they have not yet seen signs that the mosquito-born illness, now rapidly spreading through 16 other states, will do the same here.
No state was hit harder by West Nile in 2002 than Illinois, where 884 people were afflicted and 66 were killed. But as of Friday, there had been no reported human cases this year, said Tammy Leonard, spokeswoman for the state Department Public Health.
Even so, Leonard agreed with experts who warn that the potential for West Nile cases still exits, given that populations of Culex mosquitoes -- thought to be the primary carriers of West Nile -- increase later in the summer when weather is hotter and drier.
"Remember that our first human case last year was not reported until Aug. 6," Leonard said.
"We're not making any predictions, but we do expect that we will have human cases this year. Hopefully far fewer."
Since early spring, a number of local and county officials have been monitoring mosquito activity and administering abatement programs in hopes of minimizing the risk of exposure to West Nile, Leonard said.
To date, 23 birds and 28 mosquito batches in 19 counties have tested positive for West Nile virus, Leonard said. By this time last year, positive results had been found in tests on one human, 190 birds, 105 mosquito batches and three horses in 48 counties.
In Chicago, two birds and one mosquito have tested positive for the virus so far this year, said William Paul, Chicago's deputy health commissioner.
"It's really dramatic how few there are," he said.
Culex mosquitoes thrive in stagnant water but the recent rainy weather in Illinois has disrupted the puddles and pools where they lay their eggs, officials said.
Still, positive tests for the virus in mosquitoes are on the upswing, said Robert Novak, a professor of entomology with the Illinois Natural History Survey in Champaign.
He said the number of positive samples -- which had been averaging a couple a week since July 23 -- jumped to 27 this week.
"August is following a very similar pattern to what we saw last year," said Novak. He warned that officials who are tracking Culex mosquitoes should also monitor other varieties, including Aedes vexans, a flood-plain dweller that is also a West Nile carrier.
"We need all the data we can get because we don't yet fully understand a virus that has only been here since 1999," Novak said.
West Nile is transmitted through the bite of mosquitoes that feed on infected birds. Most people infected with the virus never have any symptoms, but some suffer from fever, headaches and body aches. In some of the most serious cases the virus can cause fatal brain swelling.
The disease has been spreading at a record-breaking pace in several other states, according to the Centers for Disease Control and Prevention. There have been seven deaths, four of them reported in Colorado, the hardest-hit among 16 states.
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