CDC: West Nile could spread throughout U.S.

Lab scientist Christina Bigelow and Dr. Pleasant Hooper process blood samples to be tested for the West Nile virus in New Orleans, Louisiana.

WASHINGTON (CNN) -- West Nile virus is an "emerging" epidemic that could spread throughout the United States, the director of the Centers for Disease Control and Prevention said Sunday.

"It's a problem that is having an unusually high human toll this year," Dr. Julie Gerberding said on CBS' "Face the Nation." "So it is serious, and we have to continue our public health action to combat it."

Gerberding said the population of birds infected is much broader than with most other viral infectious diseases that cause a similar type of encephalitis, so the virus spreads more efficiently.

"Wherever the birds are going, the mosquitoes are following, and that really does set the stage for transmission across the country," she said.

Gerberding's comments follow reports that two more people have died from the West Nile virus in Louisiana, bringing the number of deaths in the state so far this year to seven.

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The total number of states where the virus has been found in animals -- horses, birds or mosquitoes -- is 36, while humans have contracted the virus in six states and the District of Columbia.

The CDC has reported a total of 136 human infection cases: Louisiana (85), Mississippi (34), Texas (12), Illinois (2), Alabama (1), Indiana (1) and the District of Columbia (1).

The latest victims in Louisiana were a 76-year-old woman in St. Tammany Parish who died August 2 and a 94-year-old woman in Tangipahoa Parish who died August 4, said Dr. Erin Brewer, regional medical director for the Louisiana Office of Public Health.

Brewer said another 85 people in the state have been sickened by the virus, 59 of them with the most serious symptoms: encephalitis or meningitis or both. They are potentially fatal swellings of the brain or of the membranes that cover it. Both conditions can be fatal. Nine of the 59 are hospitalized in intensive care units.

In Indiana, a 46-year-old woman who was hospitalized for four days with flulike symptoms turned out to be infected with West Nile virus, said Dr. William Dannacher, health officer for Wabash County. She has since recovered and been discharged, he said.

At highest risk for becoming infected with the mosquito-borne virus are the elderly, those with compromised immune systems and young children.

Most infections are mild, and symptoms, which don't always appear, include fever, headache, and body aches, occasionally with skin rashes. A more severe infection may be marked by headache, high fever, neck stiffness and disorientation.

Dr. Lyle Petersen, a West Nile virus expert for the CDC, said the virus causes severe symptoms in one of every 150 people infected.

Most people get either no symptoms or milder expressions of the disease.