Zika virus is an infectious disease primarily spread through mosquito bites. It can also be:
- Transmitted through sex (i.e., anal, oral and vaginal sex; and sharing sex toys)
- Passed from pregnant women to their babies during pregnancy and birth
- Spread in other ways, including blood transfusions and tissue and organ transplants
Most individuals (about 80%) infected with Zika virus don't develop symptoms or know they are infected. When symptoms do occur they may include:
- Muscle or joint pain
- Conjunctivitis (red eyes)
- Headache — especially with pain behind the eyes
Although most of those infected with Zika virus infection will not experience noticeable symptoms, there are very significant risks associated with the disease.
According to the Centers for Disease Control and Prevention, Zika virus infection causes serious birth defects and negative pregnancy outcomes, including miscarriage, microcephaly and other "severe fetal brain defects." Microcephaly is a condition in which a baby's head and brain are underdeveloped and smaller than expected. Microcephaly can result in intellectual disabilities, hearing and vision problems, seizures, and other health concerns. Important information for pregnant women is available through the Centers for Disease Control and Prevention.
Unlike some infections, there is no vaccine against Zika virus, nor is there a specific medication to treat the infection.
Outbreak Locations and Travel Safety
Historically, Zika virus outbreaks have occurred in Africa, Southeast Asia and the Pacific Islands. Zika made its first appearance in the Americas (Brazil) in 2015 and has since spread throughout various regions of Central and South America, Mexico, and the Caribbean.
Local Zika Transmission in the U.S.
Currently, there is no local Zika transmission in the U.S. Visit the Centers for Disease Control and Prevention's (CDC) Zika in the U.S. for the latest information.
Zika and Travel Recommendations
Potential travelers (especially pregnant women, women who are planning pregnancy, and the partners of either) can refer to the CDC's Zika Travel Information for travel recommendations and information on Zika outside of the U.S.
Note: The CDC recommends that pregnant women not travel to areas with Zika.
If you will be traveling to a location with local Zika transmission
Reduce your risk of mosquito bites by using insect repellent, turning on the air conditioner in your hotel room, keeping windows and screens closed, and wearing long-sleeved shirts and long pants. If you are pregnant or trying to become pregnant, or you are a partner of either, consult with a healthcare provider prior to travel. Additional tips can be found through the CDC's Plan for Travel.
If you have recently travelled to an area with local Zika transmission
The CDC recommends watching for fever, headache, joint pain, muscle pain, conjunctivitis, or a rash appearing within two weeks of travelling. See a doctor or other healthcare provider if you become ill and inform them where you traveled.
Pregnant women who have recently traveled to an area with Zika should talk to their doctor about their travel even if they have no symptoms of Zika virus disease.
All individuals who have traveled to an area with Zika should also prevent mosquito bites for at least three weeks after returning from travel.
Because Zika can be sexually transmitted, travelers and their partners should consider not having sex or only having protected sex for at least 3 months after travel. This includes correctly using external (male) condoms, internal (female) condoms and latex dams from start to finish for every sexual encounter (anal, oral and vaginal) and not sharing sex toys (see the CDC's Sexual Transmission and Prevention Guidelines).
*For additional travel-related health information, visit the CDC's Vaccines. Medicines. Advice. For safety warnings and travel advisories, visit the U.S. Department of State.
Preventing Zika Virus Infection
For comprehensive Zika prevention information, visit the CDC's Zika Prevention and Transmission.
Prevent Mosquito Bites at Home and on Travel
The mosquitoes that transmit Zika virus not only bite during the night, they are aggressive daytime biters. These mosquitoes also spread chikungunya virus and dengue virus.* You can help protect yourself and others against mosquito bites by strictly following mosquito bite prevention guidelines, which include:
- Eliminating standing water (e.g., water in toys, flower pots, trash containers, etc.) in and around your home on a weekly basis by emptying, scrubbing (mosquito eggs stick to containers), turning over, covering, or throwing out items.
- Using air conditioning
- Using screens on windows and doors
- Correctly using an Environmental Protection Agency-registered insect repellent
- Note: Some repellents (e.g., oil of lemon eucalyptus) have age-related safety restrictions. General insect repellent use and safety information is available, but always carefully follow specific insect repellent instructions for use on babies and children.
- Wearing long sleeves
- Treating clothing and gear with permethrin according to product instructions
- Covering cribs, strollers and baby carriers with mosquito netting
- Sleeping under a mosquito bed net
*Visit the California Department of Public Health for additional information.
Prevent Zika Virus Infection During Pregnancy
- Pregnant women — no matter what trimester — should not travel to areas where Zika virus is spreading. Refer to the Centers for Disease Control and Prevention's Information for Pregnant Women and Zika Travel Information for the most up-to-date information.
- Pregnant women who have traveled to an area with local Zika virus transmission are advised to talk to their healthcare providers about their travel even if they don't have infection symptoms.
- Correctly use external (male) condoms, internal (female) condoms and latex dams from start to finish every time you have sex (anal, oral and vaginal) or don't have sex for the duration of the pregnancy.
- Avoid sharing sex toys during pregnancy.
Prevent Zika Virus Infection When Trying to Get Pregnant
- Women trying to get pregnant and their partners should talk to their healthcare providers before traveling to an area with local Zika virus transmission, and take precautions to avoid bug bites.
- Avoid trying to get pregnant (or get someone pregnant) for at least 3 months after travel to an area with local Zika transmission or after experiencing Zika symptoms. for details, visit the CDC's Women and Their Partners Trying to Get Pregnant.
- Consult a healthcare provider if one or more partners have traveled to (or lives in) an area with Zika.
Prevent Sexual Transmission of Zika Virus
Individuals infected with the Zika virus can spread Zika to their sex partners during anal, oral and vaginal sex, and through sharing sex toys — even when they don't have symptoms. Zika virus can be found in semen, vaginal secretions, blood, urine, and other body fluids. However, semen retains Zika longer than any other body fluid. Abstinence (not having sex) is the best way to prevent sexual transmission of the Zika virus.
Those at risk (travel to or living in an area with Zika) should follow the latest CDC Sexual Transmission and Prevention Guidelines which include:
Correctly using external (male) condoms, internal (female) condoms and latex dams from start to finish every time you have sex (anal, oral and vaginal)
Not sharing sex toys
Prevent Zika Virus Transmission After Travel
To prevent Zika virus infection transmission after travelling to an area with local Zika virus transmission:
- Prevent mosquito bites for at least 3 weeks after travel
- Zika virus can remain in the blood of an infected person for about a week. If the infected person is then bitten by a mosquito that mosquito may become infected with the Zika virus and then go on to infect other individuals it bites.
- Prevent sexual transmission
- Prevent Zika transmission if you have symptoms
- See your doctor if you develop Zika symptoms
- Protect yourself against mosquito bites and protect others against sexual transmission
For additional information and prevention strategies, please see these resources:
- California Department of Public Health (CDPH)
- Centers for Disease Control and Prevention