--- Indigenous. Mosquitoborne transmission of malaria in a geographic area where malaria occurs regularly.
--- Introduced. Mosquitoborne transmission of malaria from an imported case in an area where malaria does not occur regularly.

Malaria is no longer endemic in California. However, the disease is diagnosed in California residents every year, primarily as a result of contracting the disease in malarious areas outside the USA, and rarely, because of small focal outbreaks occurring as a result of importation of a case into an area when and where anopheline mosquitoes are prevalent.