Experts say recent intense and usual humidity could have fueled the rise in West Nile virus cases in Southern California.

Among the record cases are 90 neuroinvasive diagnoses - when the virus penetrates the blood-brain barrier and travels to the meninges, causing meningitis and potential paralysis.

Orange and Los Angeles counties are catching West Nile virus activity early in the season and urging residents to avoid getting bit.

After an abnormally warm winter and a blistering March heat wave, California has seen a surge in mosquito activity that has West Nile virus activity at a five-year high.

There’s no vaccine and no cure. And a wet El Niño winter could set up an even bigger mosquito boom.