California's historic drought is partly to blame for the recent rise in West Nile virus infections, public health officials say. There have been 311 cases reported so far, double the number of the same time last year, and the most of any state in the country.
West Nile virus is spread by mosquitoes. They contract the virus when they feed on infected birds, then spread it to the birds they bite next. A shortage of water can accelerate this cycle.