The number of “neuroinvasive” West Nile virus cases in California skyrocketed in 2014 and 2015, at the height of the state's most recent drought. The number of those infections in 2015 was the highest since the state began tracking the virus in 2003. Scientists say neuroinvasive West Nile virus – severe cases accompanied by meningitis, encephalitis or a type of acute paralysis – is the most accurate measure for comparing infection rates from year to year. The number of West Nile deaths fell from a high of 53 in 2015 to 10 last year.
