"While there have been no (human) deaths from WNV in San Diego County, 14 of the 15 locally acquired human cases last year (2007), were in people over the age of 50." said Gary Erbeck, director of the county's Department of Environmental Health. He continues to say that people over 50 and immunocompromised individuals are more at risk of serious complications to WNV.
The virus is passed when mosquitoes feed on infected birds or horses and then bite humans. The mosquitoes particular to this disease usually die during the winter, but a wet winter or spring have aided their survival recently which may be the cause of this early arrival of WNV.