U.S. West Nile virus cases, deaths rose in 2006

By Will Dunham

WASHINGTON (Reuters) - U.S. cases of encephalitis and meningitis caused by West Nile virus rose last year to the highest level since 2003, and the death toll jumped from 2005, federal health officials reported on Thursday.

The Centers for Disease Control and Prevention said 1,491 cases of encephalitis, meningitis and a rare syndrome caused by the virus called acute flaccid paralysis were reported in the United States in 2006.

This marked a 14-percent increase in these cases from 2005 and the largest number reported since 2003, the CDC said in a report. States with the most cases of these diseases were Texas, Idaho, Illinois, Louisiana and Mississippi.

The death toll from diseases caused by West Nile virus, which is spread by the bite of infected mosquitoes, was 177 in 2006, up from 119 in 2005.

"West Nile virus is not going away in the United States," CDC epidemiologist Mark Duffy said in a telephone interview.

West Nile virus disease first appeared in the United States in 1999. The milder form is West Nile fever, with symptoms including fever, headache, body aches, skin rash and swollen lymph glands.

If the virus enters the brain, it can cause deadly diseases including encephalitis, an inflammation of the brain, or meningitis, an inflammation of the tissue surrounding the brain and spinal cord. People over age 50 are at highest risk.

Duffy said CDC experts do not know why West Nile virus diseases are increasing.

MOST CASES SAID UNREPORTED

The CDC report was based on data from 731 counties in 43 states and Washington, D.C., accounting for 23 percent of counties nationwide.

There were 4,261 cases of disease caused by the virus in 2006, including the milder West Nile fever and the more serious forms, the CDC said.

The CDC said official reports understate West Nile fever cases, and estimated there were nearly 42,000 such cases last year, most unreported.

The state with the most overall cases was Idaho, with 996 compared to 13 in 2005, followed by Texas, Colorado, California and Nebraska. Twenty-one people died in Idaho from it in 2006, compared to none in 2005. Texas had the most deaths with 32.

The virus was detected in all 48 contiguous states for a second consecutive year.

"The best way to combat West Nile virus disease is through altering behavior, like staying indoors if possible during the evening hours when mosquitoes are active," Duffy said.