Three more U.S. states were added Thursday to the list of those reporting suspected human cases of West Nile virus, which has killed nine people in Louisiana and Mississippi in an outbreak than has spanned a dozen states.
Missouri, Ohio and Maryland are the latest states to report suspected human cases of the virus, which produces flu-like symptoms and can be deadly for the elderly and people who suffer from chronic illnesses.
Four residents of the St. Louis metropolitan area tested positive for the virus this week, two males ages 42 and 61 and two 36-year-old females, according to the St. Louis County Department of Health.
In Ohio, tests on a 25-year-old Columbus man and a 76-year-old Cleveland woman showed indications of West Nile, although lab samples have been sent to the Centers for Disease Control and Prevention for confirmation, a spokesman from the Ohio Department of Health said.
Health officials in Maryland said Thursday they are 95 percent sure that an 80-year-old Baltimore man who suffered inflammation of the brain last month could be the state's first human case of West Nile virus this year.
Preliminary tests of the man's blood and spinal fluid indicated he had contracted the virus, but final confirmation from the Maryland Department of Health and Mental Hygiene may not be come until early next week.
In a related development, the Illinois Health Department reported three new human cases of the West Nile virus on Thursday.
The cases, all in the Chicago metropolitan area, bring the state's total to five human victims of the mosquito-borne disease.
Dr. John Lumpkin, director of the Illinois Department of Public Health, said a 70-year-old man from southern Cook County was in critical condition in a hospital, suffering from West Nile encephalitis. The man became ill Aug. 4, Lumpkin said.
The other two victims, a 49-year-old woman from Will County and a 41-year-old woman from Chicago, also suffered from encephalitis but have recovered and are out of the hospital, Lumpkin said. One became ill Aug. 3 and the other first reported symptoms July 30.
Of the nine U.S. deaths related to West Nile so far this year, seven were in Louisiana and two in Mississippi, according to the CDC.
The CDC has confirmed 156 human cases in Louisiana, Mississippi, Texas, Alabama, Illinois, Florida, Indiana, Massachusetts, and the District of Columbia.
Dr. Lyle Petersen, a West Nile expert with the CDC, said the agency had about 20 staff helping officials in Louisiana, Mississippi and Arkansas identify more cases, trap birds and control mosquito populations.
Petersen noted that it was difficult to predict how many more cases would occur this year because the epidemic was largely centered in states with warm climates, in which mosquitoes thrive. But he said mosquito control would help stem the epidemic.
"We don't know, since we've never had a big epidemic in the southern United States, where the peak of the epidemic curve will actually be," Petersen said. "The bottom line is we will see more cases and potentially a lot more cases in the upcoming weeks."
The U.S. Health and Human Services Department said last week it was sending an extra $10 million via the CDC to use to fight the virus, bringing the CDC's West Nile budget to $27 million.
Various states have stepped up prevention methods, with Washington, D.C., starting efforts to kill mosquito larva as they breed and Louisiana spraying chemical pesticides.
In Chicago, city officials deployed half a dozen sewer workers on Thursday to drop larvicide tablets into the city's more than 200,000 catch basins to kill mosquitoes and prevent the spread of mosquito-borne illnesses, a spokesman from the Chicago's Department of Public Health said.
There is no human vaccine for West Nile virus, which infects birds and is spread through mosquitoes.
Most human infections are mild, and less than 1 percent of people who get bitten by an infected mosquito get severely ill. Symptoms include fever, headache, body aches, occasional skin rash and swollen lymph glands. More severe infection is marked by neck stiffness, muscle weakness and coma.