Dengue is a disease caused by any one of four closely related dengue viruses (DENV-1, DENV-2, DENV-3, and DENV-4). People get dengue from the bite of an infected mosquito. The mosquito becomes infected when it bites a person who has dengue virus in their blood. It takes a week or more for the dengue virus to replicate in the mosquito; then the mosquito can transmit the virus to another person when it bites. Dengue is transmitted principally by
Aedes aegypti (yellow fever mosquito) and
Aedes albopictus (Asian tiger mosquito). These mosquitoes are not native to California, but infestations have been identified in
multiple counties in California (PDF). Dengue virus cannot be transmitted from person to person.