Zika Virus

What everyone needs to know about Zika virus.

Contact the Epidemiology Unit

Zika Overview

Zika is a virus that is spread mostly by an infected Aedes species mosquito. Infection during pregnancy can cause certain birth defects. 

Before 2015, Zika was present in Africa, Southeast Asia, and the Pacific Islands, however, in May 2015, the Pan American Health Organization (PAHO) issued an alert about the first confirmed Zika virus infections in Brazil. Since then, Zika virus has been identified in multiple countries and territories throughout South America, Central America, and the Caribbean, as well as states in Mexico. The U.S. territory of Puerto Rico has been significantly impacted by Zika Virus. In the U.S., local transmission has been reported in Florida, and Texas.


Zika in San Diego County

All Zika cases in San Diego County have been related to travel to an area with risk of Zika. An area with risk of Zika means that mosquitoes there may be infected with Zika and spreading it to people. San Diego has also reported cases of sexual transmission of Zika from a traveler to an area with a risk of Zika, and transmission from a pregnant woman to her fetus. For updated information on Zika activity in San Diego and California, please see the  Local Zika Activity webpage.

How Zika Spreads

  • The bite of an infected Aedes species mosquito
  • From a pregnant woman to her fetus
  • Through sexual activity with an infected person 

Aedes mosquitos bite during the day and night. They prefer to bite people, and live indoors and outdoors near people. These are the same mosquitoes that spread dengue, chikungunya, and yellow fever viruses. Mosquitoes become infected, meaning they carry the virus, when they feed on a person who is already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites. Zika virus can also spread from person to person. A pregnant woman can pass Zika virus to her fetus during pregnancy, Zika can be passed through sex from a person who has Zika to his or her partner, and in Brazil there have been reports of Zika transmission from blood transfusions.

Zika and Pregnancy

The Zika virus can spread from a pregnant woman to her fetus. Infection during pregnancy can cause birth defects. In April 2016, CDC scientists announced that there is enough evidence to conclude that Zika virus infection during pregnancy is a cause of microcephaly (a birth defect where a baby’s head and brain are smaller than expected), and other severe fetal brain defects, as well as pregnancy loss, eye defects, hearing loss, and impaired growth in infants. Cases of Zika in pregnant women are reported to the U.S. Zika Pregnancy Registry

Zika Symptoms

  • Fever
  • Rash
  • Joint pain
  • Headache
  • Red eyes
  • Muscle pain 

Many people infected with Zika virus won’t have symptoms or will only have mild symptoms. Zika symptoms begin between 2 and 12 days (most commonly 3-7 days) after exposure to the virus and only last for a few days to a week. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. However, there have been cases of Guillain-Barré syndrome reported in patients following suspected Zika virus infection. 

How You Can Stop Zika

There is no vaccine or medicine for Zika. You can help stop Zika if you Prevent, Protect, and Report!

Prevent mosquito breeding sites. Mosquitos lay their eggs in standing water in things like buckets, bowls, animal dishes, flower pots, and vases. Every week, dump out and clean containers that hold water inside and outside homes. Fill plant saucers with sand or fine gravel so water won’t form pools where mosquitoes can breed.

Protect yourself from mosquito bites. Wear long sleeves and pants when outdoors. Use insect repellent with EPA-approved ingredients, such as DEET. Make sure the screens on your windows and doors are in good condition, do not have holes or tears, and are secured to keep insects out.

Report mosquito activity if you are being bitten by mosquitoes during daylight hours, or if you see black mosquitoes with white stripes on their legs and back. To report mosquito activity, please For information about how to report mosquito activity, please visit this page. A representative from the San Diego County Vector Control Program will get in touch with you within 3 business days.

What the County is doing about Zika

San Diego County is on the front line to stop the spread of the Zika virus. County public health and vector control officials continue to work with medical providers and residents to investigate potential Zika cases and take necessary precautions to minimize the chance of local transmission.


Mexican health officials have reported that mosquitoes carrying Zika virus have been found in different regions of Mexico.  These mosquitos can spread Zika to people who travel south of the border. Mosquitos that spread Zika have been reported as close as Ensenada, Baja California, about 80 miles south of San Diego.

Because Zika virus is primarily spread by mosquitoes, the CDC recommends that all travelers to Mexico protect themselves from mosquito bites, especially those who cross the border on a regular basis. It is important for travelers to protect themselves from mosquito bites after returning to the U.S. because, if a mosquito bites an infected person who is still contagious, it can spread the virus to another person.


Frequently Asked Questions

Frequently Asked Questions – Zika Virus and Mosquitoes  San Diego County – May 2017


Information for Healthcare Providers

Information for Parents (healthychildren.org)

County of San Diego Resources

California Department of Public Health 

Centers for Disease Control and Prevention Resources

For more information, contact the Epidemiology Unit at 619-692-8499 or send us an e-mail.