West Nile cases in Illinois top 500

By Gus Bode

Jackson County holds at five

West Nile virus cases have leaped by 119 since reported Sept. 17 and have been found in 518 Illinois residences since the end of July.

But even as the weather cools, health department officials expect cases and deaths of the virus to continue until November.


Illinois has almost double the human West Nile cases of any other state, although Jackson County remains free from West Nile deaths.

But the latest figures from the Center for Disease Control place Louisiana in second with more than 260 cases and Michigan in third with more than 250 cases. The same set of figures show Illinois has more deaths than any two other states combined. The virus has been found in 98 of Illinois’ 102 counties.

The first West Nile case in Illinois was discovered in a 22-year-old student from Maryland who was living in Cook County. Eleven men and 16 women from Illinois have died from the virus since Aug. 10, when a 67-year-old DuPage County man died from West Nile encephalitis. He was hospitalized Aug. 4 after experiencing fever, stiff neck, and changes in consciousness.

Because those with weakened immune systems are more susceptible to contracting the virus, the average age of Illinois residents who have died from the virus is 78. The youngest person to die from the virus was 64.

West Nile is not the first virus to hit Illinois hard. St. Louis encephalitis, a close relative to West Nile encephalitis, hit Illinois worse than any other state in the nation in 1975. Illinois had 578 cases of the virus and 48 deaths resulting from infection. The nation had about 2,000 cases of St. Louis encephalitis that year.

West Nile virus has similar figures. The state is 60 cases short of the 1975 level and has 19 fewer deaths. There have been about 2,000 West Nile virus cases in the nation.

Tom Schafer, a spokesman for the Illinois Department of Public Health, is uncertain why the Midwest has seen so many cases. He said the department was anticipating human cases this year but had no idea there would be so many.


The West Nile virus is carried by mosquitoes and causes West Nile encephalitis, inflammation of the brain, and meningitis, inflammation of central nervous system membranes. Symptoms can be mild or severe and include headache, fever, stiff neck, stupor, convulsions, muscle weakness, paralysis and, in a person who is older or has a weakened immune system, neurological damage or death. Antibiotics are not effective against the viral infection, and a specific treatment has not been developed. Most people infected with the virus will experience little or no symptoms

The virus is typically spread by the Northern House Mosquito, but other mosquitoes can still carry it. The Northern House Mosquito is prevalent in all areas of Illinois and is one of the most common types.

Schafer said the health department is seeing decreased mosquito activity. He said the decrease could be a combination of mosquito control efforts and colder weather.

“When it starts getting colder, rather than feeding on humans and mammals for blood, they start gathering sugar for hibernation,” Schafer said.

Schafer said it is a misconception that more rain leads to more mosquitoes. He said the insects can breed in small pools of water, especially pools that are stagnant for a week or more. Mosquitoes usually require a week to 10 days to hatch into adults and more rain can keep water moving and wash away breeding areas. Temperatures below 50 degrees can extend the growth period to several weeks.

Schafer said rain can still have an impact in the mosquito population that carries West Nile, but other “nuisance” mosquitoes that do not tend to carry the virus hatch about a week after rains.

Miriam Link-Mullison, administrator for the Jackson County Health Department, said recent rains are a need for increased diligence because pools of stagnant water are not being flushed out during the drought.

Mosquito activity is not expected to decrease until after the first hard frost.

“We expect the activity to continue for the next month and a half or so,” said Link-Mullison.

The Jackson County Health Department will continue work on mosquito control through the winter by collecting used tires, a common breeding ground for mosquitoes, finding breeding grounds and preparing for next summer.

The county has focused on eliminating collections of used tires in the past because they collect water and are commonly overlooked as a mosquito breeding site. Link-Mullison said tires have been a primary concern for the last several years because of mosquito carried illnesses other than West Nile. The last collection by the county took place in September 2001.

The most effective method to control the mosquito population is to kill the insects before they develop into adults. Reducing standing water and applying larvicides are more effective than spraying or fogging for mosquitoes, which kill the adults of the species.

Local municipalities have mosquito abatement departments and the Jackson County Health Department is focusing its efforts on unincorporated areas of the county.

The weather patterns of the past year closely resemble those of 1975, when St. Louis encephalitis was at its worst. Both years had a mild winter and a summer drought and very similar case counts.

“The numbers are going to come out very close,” Link-Mullison said. “I find those to be amazingly close numbers.”

Link-Mullison said people should not request testing for the virus for mild flu-like symptoms. She said there is no advantage to knowing if an illness is West Nile in mild cases. Symptoms should be treated the same as a flu.

“If you’re seriously ill and hospitalized, they will probably test you,” Link Mullison said.

The cooling weather will not likely immediately halt the virus. Link-Mullison said there will still be cases and deaths from the virus into November.

The West Nile virus has an incubation period of three to 14 days, meaning a person may not experience symptoms for two weeks after being infected.

Reporter Greg Cima can be reached at [email protected]