Zika Virus

What to know about Zika virus

Zika virus was first identified 1947 and is named after the Zika Forest in Uganda. The first human cases were documented in 1952.  Since it’s discovery, the virus has been found in both mosquitoes and humans in Africa, the Pacific Islands, Southeast Asia, and the Americas.

Zika is spread to people primarily through the bite of an infected Aedes aegypti or Aedes albopictus mosquito. These mosquitoes are not from California but have been found in many areas in the state, such as Southern California and the Central valley.

Although Ae. aegypti mosquitoes have been found in Alameda County since 2024, there is no current local transmission of Zika virus in the continental United States. To date, all cases of Zika in Alameda County have been travel-associated, meaning they acquired their infection when traveling outside of California. 

For questions, consultations, or to report unusual mosquito activity, contact the Alameda County Mosquito Abatement District at 510-783-7744. District staff can help residents identify mosquitoes, eliminate breeding sources, and stay informed about local mosquito activity.

Human health effects:

  • About 1 in 5 people with the Zika virus will have symptoms.
  • The most common symptoms are fever, joint pain, rash or red eyes.
  • Symptoms are normally mild and may last up to a week.
  • Hospitalization is uncommon and deaths are rare.
  • The CDC has confirmed a link between Zika virus and microcephaly (abnormally small head) in newborns. Pregnant women who get the virus are at risk of the fetal birth defect.

Zika virus has not been found in mosquitoes in Alameda County.  When traveling to areas with virus activity, please make sure to take proper precautions.

Protect yourself from mosquito bites:

Properly use mosquito repellents containing DEET, Picaridin, IR3535, PMD, or oil of lemon eucalyptus (always read the label carefully).

  • Wear protective clothing such as long sleeves and long pants.
  • Consider treating clothing with permethrin or buying clothing treated with permethrin.
  • Stay and sleep in screened-in or air-conditioned rooms. If not possible, use a bed net.
  • Before traveling check the CDC’s Travelers Health website (http://www.cdc.gov/travel) for information regarding the specific area(s) you will be visiting.

For more information on Zika virus:

California Department of Public Health (CDPH) | Zika

Centers for Disease Control and Prevention (CDC) | Zika Virus