Doctors in the U.S. should proactively screen at-risk pregnant women for the Zika virus, according to the Centers for Disease Control and Prevention. “All pregnant women in the United States and U.S. territories should be assessed for possible Zika virus exposure at each prenatal care visit,” reads a new memo the CDC released on Monday.
That’s the most aggressive recommendation yet to come from the CDC in the past several months of mounting preparation for Zika’s landfall in the continental U.S. It doesn’t mean that doctors must test all pregnant patients for Zika, but that they should discuss risk factors—travel to a Zika-afflicted area, a symptomatic partner—to determine the need for further testing.
The new guidelines also broaden the population of patients for whom testing is recommended. It used to be that a pregnant patient or her sexual partner had to travel to an area in the current Zika danger zones and develop symptoms before the CDC would unequivocally recommend testing. Now, in part because about 80 percent of Zika-infected people don’t end up showing symptoms of the virus, the CDC also recommends testing some asymptomatic pregnant women, too. If a patient might have been exposed to Zika through travel or a traveling sexual partner, the CDC now says a doctor should offer her a test even if she exhibits no symptoms.
The CDC has also highlighted the importance of timely Zika testing using multiple methods. Kaiser Health News reports:
Both symptomatic and asymptomatic pregnant women should be screened within two weeks of the date of possible Zika exposure through a DNA-based test known as PCR. PCR has been in use already, but until recently, was believed to only work within one week of exposure. If the PCR test turns up negative or an at-risk pregnant woman missed that initial two-week window, the CDC calls for screening with a test that searches for antibodies the virus produces. That test, which is effective for as long as 12 weeks after exposure, is considered a less reliable indicator and has drawn some criticism because it can generate false positives.
According to the new memo, “emerging data” suggests that Zika RNA can be detected in some pregnant women for longer than that initial one-week window, which makes the more reliable PCR test a far preferable option. The CDC has reemphasized how critical it is that doctors test pregnant women within a short period of time following potential exposure to try to catch the virus on the PCR test.
It may be another month or two before Zika begins to spread by mosquito in the Gulf Coast region, where it’s expected to hit first and worst. If researchers do develop a vaccine, it won’t become available until months later. Until then thorough conversations and vigilant screening are the best doctors can do to prevent the devastating effects of the virus on pregnant women and their fetuses.