Encephalitis from West Nile Who's at risk?

MADISON, Wisconsin, Aug 18 (Reuters) A new study pinpoints several risk factors for developing deadly encephalitis (inflammation of the brain) caused by mosquito-borne West Nile virus infection.

Researchers took a look back at the hospital charts of 172 people with West Nile infection, including 113 cases of encephalitis (including 17 deaths), 47 of meningitis and 12 with uncomplicated fever. The median age of the hospitalised cases was 54, and the median age of those who died was 75 (range 47-95).

The researchers identified older age, history of heart and vascular disease, and history of hypertension (high blood pressure) as independent risk factors for developing encephalitis from West Nile infection.

In a presentation of the findings to the International Conference on Diseases in Nature Communicable to Man, in Madison, Wisconsin, Dr Kristy Murray, of the University of Texas Health Science Center, Houston, suggested that high blood pressure might make it easier for the virus to enter the brain.

After adjusting for age, a suppressed immune system, being African-American, being infected with hepatitis C virus and having kidney disease all raised the risk of death from West Nile-associated encephalitis.

According to the Centers for Disease Control and Prevention, up to 20 per cent of people who become infected with West Nile virus develop symptoms such as fever, headache and body aches, nausea, vomiting, swollen glands or skin rash.

About 1 per cent of people infected with West Nile will develop severe illness, including high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. If the virus enters the brain, it can cause encephalitis or meningitis.

In the current case series, 42 per cent of patients were still reporting symptoms related to West Nile virus infection 3 years post-onset.

REUTERS RAR VV0916