The Centers for Disease Control and Prevention (CDC) today issued a Health Alert Notice with updated guidance for healthcare professionals to interpret Zika test results for women who live in, or frequently travel (daily or weekly) to areas with a CDC Zika travel notice.

This change is being made because CDC’s Zika testing guidance for pregnant women relies, in part, on a test [Zika virus Immunoglobulin M (IgM) ELISA] to detect Zika antibodies or proteins that the body makes to fight Zika infections. New data suggest that Zika virus infection, similar to some other flavivirus infections, may result in Zika antibodies staying in the body for months after infection for some individuals. As a result, results of these tests may not be able to determine whether women were infected before or after they became pregnant.

Specifically, CDC recommends the following guidance for healthcare professionals evaluating women without symptoms who had potential Zika exposure—particularly women who live in or frequently travel (daily or weekly) to areas with CDC Zika travel notices. Use of these tests may be helpful, but may not always be conclusive, in distinguishing how recent the infection is.

Screen pregnant women for risk of Zika exposure and symptoms of Zika. Test pregnant women promptly, using nucleic acid testing (NAT), if they develop symptoms at any point during pregnancy or if their sexual partner tests positive for Zika virus infection;

Consider NAT testing at least once during each trimester of pregnancy to detect evidence of Zika virus, unless a previous test has been positive;

Consider testing specimens obtained during amniocentesis to detect evidence of Zika virus if amniocentesis is performed for other reasons;

Counsel all pregnant women each trimester about the limitations of Zika testing.

“Our guidance today is part of our continued effort to share data for public health action as quickly as possible,” said Henry Walke, M.D., incident manager of the agency’s Zika response efforts. “As we learn more about the limitations of antibody testing, we continue to update our guidance to ensure that healthcare professionals have the latest information for counseling patients who are infected with Zika during pregnancy.”

For women planning to become pregnant who might have been exposed to Zika previously, healthcare professionals can consider testing for Zika antibodies before pregnancy. Antibody test results before pregnancy should not be used to determine if it is safe for a woman to become pregnant. Rather, testing before pregnancy can help determine whether a woman becomes infected during pregnancy. For example, if a woman has a negative result before pregnancy and a positive result when she is tested during pregnancy, it is more likely that the woman experienced an infection during pregnancy.

The CDC guidance also notes that test results represent a single point in time. Women who live in areas with a CDC Zika travel notice and who have never been infected with Zika virus are at continued risk of getting Zika.

To prevent Zika, CDC recommends the following steps:

Women and men who live in or travel to areas with a CDC Zika travel notice should be aware that these areas have ongoing Zika virus transmission. Those who are pregnant or have a pregnant sex partner should consistently and correctly use condoms to prevent Zika during sex or should not have sex during the pregnancy.

Pregnant women and their partners living in or traveling to areas with a CDC Zika travel notice should be aware that mosquitoes in these areas can spread Zika. They should strictly follow steps to prevent mosquito bites.

For information on geographic areas with Zika transmission, visit Areas with Risk of Zika. For the most current information about Zika virus, visit http://www.cdc.gov/zika/. Also, to see a searchable database of specialists available in several states, the U.S. Virgin Islands, and Puerto Rico, visit http://www.zikacareconnect.org/.