فيروس غرب النيل
In 2011, the Greater Los Angeles Area experienced an epidemic West Nile virus year, with activity levels almost reaching those recorded for 2004 and 2008. The California Department of Public Health documented 158 West Nile virus human cases with 9 of those cases resulting in fatalities. In September 2011, an infestation of the Asian tiger mosquito was discovered in the San Gabriel Valley.