Updated guidance from the Centers for Disease Control and Prevention (CDC) instructs physicians to test pregnant women for Zika up to 14 days after symptoms begin. It also adds new recommendations based on the first documented female-to-male transmission of the virus.

The previous CDC instructions suggested Zika-specific blood tests be conducted within a week after pregnant women show signs of the mosquito-borne virus, but the agency now says tests of some infected women show evidence of the virus in blood tests taken after the seven-day window. The new guidance recommends testing for pregnant women who may have been exposed to Zika, even if they aren’t showing symptoms.

The agency says this will help provide an alternative to a different, less accurate test taken after seven days looking for evidence the body is fighting a family of viruses that may include Zika.

“If pregnant women visit their healthcare provider after the 14-day testing window and test positive with the less-specific test, the Zika-specific blood testing can now be offered potentially to provide a definite diagnosis for pregnant women with Zika virus infection,” the CDC says. “Expanding the use of the Zika-specific test could provide more women with Zika virus infection a definite diagnosis and help direct medical evaluation and care.” 

The second article of the updated guidance deals with the July 15 discovery by the CDC that the virus could be sexually transmitted from a female to a male.

“Although transmission of Zika from a woman to her sex partners is believed to be uncommon and (as with the majority of Zika infections) unlikely to result in serious side effects, it could present a risk for pregnant women with female sex partners who may be infected with Zika,” the CDC says. “For this reason, CDC recommends that all pregnant women with sex partners (male or female) who live in or traveled to an area with Zika use condoms during sex or abstain from sex for the remainder of their pregnancy. All other couples in which a partner (male or female) has been in an area with Zika can also reduce the risk of sexual transmission by using condoms or abstaining from sex.”

The guidance says providers should test any patients with Zika symptoms and report potential sexual transmission to a partner who lives in or traveled to an area where Zika has been prevalent.

The CDC only confirmed in February that Zika can be transmitted sexually. As of July 14, 400 pregnant women in the U.S., along with another 378 in its territories, have lab evidence of a Zika infection. While approximately one-fifth of those infected show no symptoms, the virus can cause serious birth defects, such as microcephaly. While all cases so far have been related to travel, the Miami Herald reported the Florida Department of Public Health is investigating two possible cases of local transmission from mosquitos.