West Nile has claimed two more victims, one in Illinois and another in Louisiana, bringing this year's death toll from the rapidly spreading virus to 11 nationwide.
A 78-year-old man became the eighth fatality in Louisiana, where the mosquito-borne disease has hit hardest. The state also reported 62 new human cases, bringing its total this year to 147 in the worst outbreak since the ailment was first detected in the United States three years ago.
Across the country, 251 human cases have been reported, the Centers for Disease Control and Prevention said.
"An epidemic this size is like a hurricane. What you need to do is take shelter," said Louisiana state epidemiologist Raoult Ratard. "If you don't take shelter you may be swept away."
"Taking shelter" in the case of mosquito-bourne viruses means using mosquito repellent and making sure residents' yards are free of standing water to ward off the virus, he said.
The virus has spread rapidly since it was first detected in 1999 in New York. It killed 18 people from 1999 through 2001, according to the CDC.
This year, two people died in Mississippi, in addition to the deaths in Louisiana and Illinois.
In Illinois' first human death linked to West Nile, a 67-year-old man died of encephalitis Aug. 10 after being admitted to the hospital with the virus, state health director John Lumpkin said. The state also reported three non-fatal cases in the Chicago area.
"The results are very serious, but we want to remind people that this is still a very rare disease among people bitten by mosquitos," Lumpkin said.
The virus has been found in every state east of the Rocky Mountains, with states as far west as Colorado and Wyoming saying they have confirmed animal cases.
Michigan reported its first human case of West Nile on Friday, and in Rochester, N.Y., a zoo penguin died from the virus, officials said.
A CDC West Nile expert, Dr. Lyle Petersen, said the disease's peak this year may not come for several weeks, and predicted 1,000 people could be infected this year and 100 could die.
The previous high for West Nile, 62 cases and seven deaths, was in New York City in 1999. From that year through 2001, the CDC confirmed 149 human cases and 18 deaths.
CDC Director Dr. Julie Gerberding has said birds and mosquitoes could spread the virus to the Pacific Coast.
Still, health officials worked to calm public fears. In Texas, one of the hardest-hit states with 16 human cases, Houston health officials hope to publicize prevention methods without causing panic.
"We're not trying to alarm people," said Sandy Kachur of the Harris County Public Health Services. "We tell people in the summertime they always need to wear sunscreen when they go outside. Now it looks like it's almost going to be that way with insect repellent, too."
Most people who get the disease experience mild flu-like symptoms, or no symptoms at all. But it can cause encephalitis, a potentially fatal swelling of the brain, especially in older people and those with weakened immune systems.