This comes in just as health officials said today that a San Fernando Valley man is the first this year from Los Angeles County to die of West Nile. He was in his 80s.

Now a new study pinpoints several risk factors for developing deadly encephalitis (inflammation of the brain) caused by mosquito-borne West Nile virus infection, according to Reuters today.

Older adults with a history of heart and vascular disease and those with high blood pressure seem to be the ones who become sickest, researchers say.

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.

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 hospitalized cases was 54, and the median age of those who died was 75 (range 47-95).