The worst outbreak of West Nile virus in U.S. history has killed seven people in Louisiana, and Mississippi officials fear a death there may be the eighth linked to the virus this year. Mississippi Gov. Ronnie Musgrove on Friday declared a state of emergency, clearing the way to seek federal funding to fight the outbreak.

Louisiana, which reported its sixth and seventh West Nile virus deaths on Friday, had already taken that step. The latest victims were identified as a 76-year-old woman who died Aug. 2 and a 94-year-old woman who died on Sunday. Both lived north of New Orleans, across Lake Pontchartrain.

``It looks like a lot of the people who died were elderly people and people with other health problems,'' said Dr. Raoult Ratard, Louisiana's state epidemiologist.

West Nile virus was first detected in the United States in 1999, when seven people died and 55 others were hospitalized in New York.

With weeks of hot, sticky weather ahead, Louisiana has already equaled the death toll from that outbreak, and there have been 85 confirmed human cases in the state, 59 of them involving encephalitis, a potentially deadly inflammation of the brain.

Officials are still waiting for test results on 90 other blood samples, Ratard said. To get faster results for the most seriously ill, Louisiana plans to test only people who appear to have nervous system infections — meningitis or encephalitis.

In an attempt to stem the spread, Sen. Mary Landrieu, D-La., said she planned to ask the Air Force next week to send in a special operations squadron to spray insecticide in hard-hit regions. The operations group of the 910th Flight Wing, based in Ohio, specializes in insect control.

Since it appeared in the United States, the virus has been detected in 35 states and Washington.

A Centers for Disease Control and Prevention report released Thursday said there had been at least 112 human cases of the mosquito-borne virus this year — more than half of them in the past week. After the report was written, human cases were reported in Indiana, Alabama and Washington, D.C. Mississippi has reported 41 human cases, and there have been cases in Texas and Illinois.

Animal cases have spread all the way to western Nebraska.

South Dakota officials said the virus showed up in four pelicans that apparently died of something else. State epidemiologist Lon Kightlinger said it was the first time the disease was found in the big birds in the United States.

The CDC has already given $17 million to states to fight against mosquitoes, but said an additional $10 million will be handed out. About $3.7 million will be earmarked for Louisiana and Mississippi.

Most people bitten by an infected mosquito will suffer no more than flu-like symptoms, but the weak and the elderly can get encephalitis. Officials in a number of states have boosted mosquito-spraying and urged people to protect themselves by using bug repellent and wearing long sleeves.

Encephalitis is usually seen in August and September, but Louisiana's first patients became ill in June. The West Nile virus is showing up earlier as it spreads to warmer climates, according to the CDC.