A North Hollywood woman has contracted the county's first case of St. Louis encephalitis this year, health officials said. The virus, which is transmitted by mosquito bites, first struck Southern California last year, with 26 cases reported. A 62-year-old Long Beach woman died as a result of the virus. St. Louis encephalitis is a viral inflammation of the brain and central nervous system that is not always fatal. Health officials said they do not expect an outbreak of encephalitis this year because recent cooler weather has suppressed mosquito activity.