Frequently Asked Questions About Zika Virus

Pregnant woman

If you're currently expecting a baby or plan on becoming pregnant soon, the Zika virus is probably on your mind. Here are answers to some common concerns about Zika, based on what we currently know about the disease.
We will update this page as we learn more, so please check back.

What is Zika?

Zika is a virus in the same family as yellow fever, dengue, West Nile and Japanese encephalitis viruses. Zika virus mostly seems to attack cells in the nervous system.

How is Zika transmitted?

Zika is most commonly contracted from the bite of an Aedes mosquito. It also can be transmitted sexually through vaginal, anal and possibly oral sex.

A pregnant woman also can pass the virus to her fetus in utero. There is a possibility that Zika can be transmitted from blood transfusions, but precautions have been taken to make sure the blood supply is safe.

There is no evidence at this time that Zika virus is passed through breast milk.

What are the symptoms of Zika virus?

Most people (80 percent) don't experience any symptoms from Zika virus. Those who do may experience one or more of the following:

  • Fever
  • Rash
  • Joint pain
  • Eye redness or inflammation

Symptoms usually begin about a week after exposure to the virus and last a few days to a week. If you or your partner experience these symptoms after visiting an area with active Zika transmission, contact your health care provider right away.

What other problems can Zika virus cause?

Zika virus may cause birth defects if a fetus becomes infected. The virus can prevent normal brain development and may cause microcephaly, which is an abnormally small head size. Zika infection of a fetus may also lead to hearing, vision, cognitive and developmental disorders.

Scientists are still investigating the range of effects that Zika virus may have on a fetus.

Adults who become infected with Zika may develop a rare neurological complication called Guillain-Barré syndrome. This is a condition that can cause temporary paralysis and may be severe enough to require extended time in the hospital with breathing support. Most people recover, but it can take several months for muscle function to be restored.

Am I at risk for getting Zika virus?

You may be at risk for Zika if you travel to an area where there is local transmission of the virus. This means mosquitoes in the area may be carrying the Zika virus and are capable of passing it to people when they bite. There may also be a risk if you have unprotected sex with a partner who has traveled to a Zika area.

The list of regions where local transmission of Zika has been reported is being updated regularly. It is most common in Central and South America, the Caribbean and parts of Africa and Southeast Asia. In the United States, there were previous reports of local transmission in Miami and Brownsville, Texas. Check the CDC website for the complete list of travel advisories.

Could there be local transmission of Zika virus in the San Francisco Bay Area?

It is not known exactly if or when local transmission of Zika will occur in California. The Bay Area does have the two types of Aedes mosquitoes that can potentially carry the Zika virus, but there have been no reports of infections from local mosquitoes. While it is possible that there will be local transmission, a widespread outbreak is very unlikely.

How can I prevent Zika virus?

There currently is no vaccine to prevent Zika virus and there are no known treatments. The best way to prevent Zika virus is to avoid mosquito bites.

To prevent the possibility of sexual transmission, abstain from sexual activity. Use latex condoms to reduce the risk of sexual transmission from a partner who may have been exposed to the virus.

How can I prevent mosquito bites?

The mosquitoes that spread Zika virus bite both during the day and at night. When traveling or during mosquito season:

The active ingredients in most EPA-regulated repellents are: DEET; Picaridin; IR3535; or oil of lemon eucalyptus. The percentage of DEET determines how long the repellent lasts, not its effectiveness. Always reapply mosquito repellent according to the directions on the package.

If I traveled, should I get tested for Zika?

If you have traveled to an area of Zika risk, you can be tested.

A test called an RT-PCR will check for the virus in your blood and urine if it has been two weeks or less since you may have been exposed to Zika. If two to 12 weeks have passed since a possible exposure, we can perform a test to see if your body produced IgM antibodies to the virus.

There are no tests currently available to determine if there was Zika exposure more than 12 weeks in the past, or if a person has immunity.

What if my partner traveled?

Partners should consult their primary care providers to arrange testing if they experienced Zika symptoms. Partners of pregnant patients or couples looking to get pregnant should contact the Zika Response Nurse Coordinator to discuss testing options.

My partner traveled but did not have symptoms. Do I need to take any precautions?

If your partner traveled to a Zika area and you are pregnant, it is recommended that you abstain from sex to avoid sexual transmission, or use latex condoms for the duration of the pregnancy to reduce the risk of sexual transmission.

I am not pregnant now but want to become pregnant. What precautions do I need to take?

If you wish to become pregnant and have traveled to an area with active Zika transmission, it is recommended that you wait eight weeks before trying to conceive, regardless of whether you had symptoms of Zika or not. If your partner traveled to a Zika area, the recommendation is to wait six months before trying to conceive. This is because the virus is known to live longer in semen, and there is a risk that men who were exposed to Zika could sexually transmit the virus for a longer period of time.

How will my prenatal care be different if there is the possibility I was exposed to Zika virus?

To assess your risk for Zika virus, you will be asked at every UCSF prenatal visit if you or your partner have traveled. If you qualify for testing, we will schedule a telehealth (video) visit with a nurse practitioner specializing in Zika management to arrange testing and answer all of your questions. A negative antibody test result means you can continue with routine prenatal care, and no further follow-up related to Zika is necessary.

If you may have been exposed to Zika virus, but it has been more than 12 weeks since you or your partner returned from travel, we can conduct periodic ultrasounds after 20 weeks gestation to assess fetal growth. If you test positive for Zika, or your fetus shows signs of abnormalities that may be related to Zika-virus exposure, one of our high-risk, maternal-fetal medicine doctors will follow your care.

If I test positive for Zika, what are the chances my fetus is infected and when will I know?

There is a lot we do not know about why some fetuses become infected with Zika virus and why others do not. The most recent research suggests that the rate of infection for a fetus may be between 1 and 13 percent if a pregnant woman is infected in the first trimester. Researchers currently believe it is less likely a fetus will become infected in the second and third trimesters, but more research is needed before this can be determined.

There is no specific gestational age at which a fetus shows Zika-related abnormalities. Sometimes the signs of infection do not appear until late in the second or third trimester. Not all fetal abnormalities associated with Zika virus can be detected with an ultrasound examination.

What if I have more questions?

If you are a patient with UCSF Obstetrics, please call 415-353-2566 to arrange a telehealth visit with the Zika Response Nurse Coordinator. You can also visit the CDC Mother-To-Baby website to call, chat with, text or email an expert for more information about Zika virus and mother-fetal transmission risks.


Reviewed by health care specialists at UCSF Medical Center.

This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.