WASHINGTON -- Louisiana Governor Mike Foster has declared a state of emergency and requested Federal assistance, after an outbreak of West Nile Virus claimed four lives in the southern U.S. state and the number of those affected by the disease reached 58.

"It is becoming quite evident that the broad nature of this outbreak is going to quickly deplete both state and local funds dedicated to epidemiological efforts, laboratory testing, surveillance and mosquito control efforts," said David Hood, secretary of the state Department of Health and Hospitals.

The declaration came on Friday, after authorities registered three more fatal cases of the disease in various parts of the state.

Twenty-six more people infected by the virus have been identified in just one day, according to state health officials.

An 83-year-old woman from the city of Baton Rouge, whose name has not been released, died from West Nile Virus earlier in the week.

On radio, state officials urged the population to stay away from stagnant water, breeding grounds for mosquitoes that carry the virus.

Pick-up trucks spewing insecticide could be seen Friday on many Louisiana highways.

The Atlanta, Georgia-based Centers for Disease Control and Prevention (CDC) has dispatched a team of experts to the state to plot anti-mosquito strategy.

But getting rid of the insects could prove to be a tall order for the low-lying state, which is crisscrossed by swamps, bayous and rivulets that form the Mississippi Delta.

West Nile virus made its north American debut in 1999 in New York, where it is believed to have been brought by individuals returning from trips to Africa.

That epidemic affected a total of about 60 people and claimed seven lives.

Healthy people infected by it show only flu-like symptoms, but the infection could lead to deadly West Nile virus encephalitis among young children, the elderly as well as people with suppressed immune systems.

The Louisiana outbreak shows that despite the government's best efforts to contain the disease, West Nile virus has now spread far beyond the eastern seaboard and is now affecting practically the whole eastern part of the United States.

In addition, five cases of the virus have been registered in Mississippi and eight in Texas, according to CDC officials.

Animal infections have been reported in nine states, including Georgia, Florida, Kentucky, Louisiana, Minnesota, Mississippi, North Dakota, Texas and South Dakota.

And, to the dismay of secret service officials, an infected dead crow was discovered last week on a White House lawn.

Since the disease is often carried by migratory birds, preventing its further movement across the country could be difficult, according to Anthony Marfin, the CDC's top expert in West Nile virus.

"There has been a great deal of speculation as to how far west the West Nile virus will spread," Marfin told AFP. "I think that a lot of people are expecting great movement because of what we've seen in the past year."