(CNN) -- An Illinois man died from West Nile complications over the weekend as the United States battles its biggest spike in the virus since 2004.
William J. Mueller was hospitalized for two weeks and died Saturday, according to the website for the village of Lombard, a Chicago suburb.
Mueller, 76, was Lombard's president, a post he held for almost two decades.
This year's U.S. outbreak of West Nile, which is spread through infected mosquitoes, is one of the worst since the virus was first detected in the United States in 1999, the U.S. Centers for Disease Control and Prevention said.
At least 26 deaths and 693 cases in 32 states have been reported nationwide as of Tuesday evening, the CDC said.
A West Nile virus epidemic in Texas prompted a judge to declare a state of emergency in Dallas County, where the disease has killed at least nine people. Insecticide spraying from planes will be offered to certain communities hit hard by the virus.
"Dallas had a very mild winter, we had a lot of rain -- we were very thankful for all the rain, because we had been part of the drought last year -- (but) that combination is going to create a higher mosquito population," Dallas Mayor Mike Rawlings told CNN.
Ebonie Conner is the mother of one of the Texas victims, 14-year-old Jordan, who is now being treated for West Nile symptoms. There are no medications to treat the virus or vaccines to prevent infection.
"The symptoms play peek-a-boo with you," she told CNN, noting that her daughter's symptoms began with a headache.
"Jordan has never really said she had a headache, so when the mention of a headache became complaint of a headache, I was very concerned. And when the complaint included vomiting -- well, the next day we had a doctor's appointment."
They couldn't wait for the doctor's appointment. Jordan lapsed out of consciousness that night, so Conner took her daughter to the emergency room.
Texas, Mississippi and Oklahoma have reported the most West Nile infections in people, birds or mosquitoes, according to the CDC, which lists a breakdown of infections by state.
"It is not clear why we are seeing more activity than in recent years," said Marc Fischer, a medical epidemiologist at the CDC. "Regardless of the reasons for the increase, people should be aware of the West Nile virus activity in their area and take action to protect themselves and their family."
Rawlings is advising Dallas residents to wear long sleeves, dark clothes and an insect repellent containing DEET.
"Don't go out at dusk," he warned. "That's when the most (mosquito) activity is there."
In the United States, most infections occur from June to September and peak in August, according to the CDC.
Symptoms include fever, headache, body aches, joint pains, vomiting, diarrhea or rash, the CDC said.
People older than 50 and those with conditions such as cancer, diabetes and kidney disease or with organ transplants are at greater risk.
Those with milder illnesses typically recover on their own, but those more seriously affected may need hospital care.
Health experts say prevention measures include using insect repellent and getting rid of mosquito breeding sites.
Conner said she never expected West Nile to be an issue for her family.
"We were just the most unlikely people that it could happen to," Conner said. "We weren't by standing water, and the kids weren't outside."
Amara Durham, a spokeswoman for Caron Texas, an alcohol and drug rehabilitation center north of Dallas, says she has a close friend who is now affected by the virus.
"I am no longer cavalier about this," Durham said.
The center where she works is also taking precautions with its patients, she said.
"We've adjusted our schedules so that patients aren't out at dawn or dusk," Durham said. "We're providing appropriate mosquito repellent. We're telling our patients what ... to wear to avoid being bitten. We're suspending activities near our lake.
"We've done a lot for preventative measures as a business within a community impacted by it."
CNN's Nick Valencia contributed to this report.