Faced with growing concern over a mosquito-borne virus known as Zika, public health officials on Tuesday outlined new guidance for pregnant women who have traveled to affected regions and for their doctors.

Zika infections in pregnancy are believed to increase the risk of a potentially devastating birth defect. Babies born with the condition — known as microcephaly — have smaller-than-normal heads and may have under-developed brains. Brazil, which has been experiencing a Zika outbreak since last May, has reported a 20-fold rise in cases of microcephaly, beginning in October.

Proof of the need for guidance for health-care providers was swift. Health officials in Illinois announced Tuesday that two pregnant women from that state who had recently travelled to a country with ongoing Zika virus transmission had tested positive for the infection. Their health is being monitored.

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The Centers for Disease Control and Prevention on Friday urged pregnant women not to travel to places where transmission of the virus is ongoing, if they can avoid it. It listed 13 countries in the Americas, as well as Puerto Rico — where someone who had not travelled became ill late last year.

The travel warnings do not apply to places where Zika cases are detected in people who have returned from travel abroad. Media reports Tuesday suggested Florida has recently found three such cases, in Dade and Hillsborough counties. Recently Houston also reported a case in a returning traveler.

On Tuesday, the CDC and the American College of Obstetricians and Gynecologists said they were issuing new interim guidance aimed at helping doctors and other health-care providers cope with the new situation.

Zika virus, which can be transmitted by mosquitos, has exploded onto the world stage in recent weeks. Alex Hogan/STAT

“I think people are rapidly becoming aware of Zika. …We are receiving a lot of queries,” said Dr. Denise Jamieson, a medical officer with the CDC’s division of reproductive health. “Pregnant women and their healthcare providers are looking for information.” 

For pregnant women, the advice boils down to two recommendations. Don’t visit places experiencing Zika virus outbreaks if you can avoid doing so. Do everything you can to avoid being bitten by mosquitoes if you must travel to one of the affected places.  

The insects that transmit Zika virus are day-biting mosquitoes and they like to live in and around houses.

The CDC advises wearing long sleeved clothing, long pants, using permethrin-treated clothing and gear, using effective insect repellents, and sleeping in screened-in or air-conditioned rooms. Products containing DEET, picaridin, and IR3535 are safe for pregnant women when used according to label instructions, it notes. 

“I realize that pregnant women are often afraid to use medications and other interventions in pregnancy. But what they should realize is that there are often risks of not doing anything,” Jamieson said. 

“So being in a Zika-affected area and not using insect repellant is risky.”

The guidance for health-care providers stipulates that they should ask pregnant women in their care whether they have recently traveled to a location where the Zika virus is spreading.

No additional testing is recommended if a pregnant woman has not traveled to one of the affected locations. However, if a woman has traveled to a Zika-affected area during her pregnancy and if she reports having two or more symptoms consistent with the illness within two weeks of travel, she should be tested for Zika, the guidance states.

CDC
Countries that have past or current evidence of Zika virus transmission. CDC

Symptoms include acute onset of fever, a raised, red skin rash, joint pain or conjunctivitis, sometimes called pink eye. If ultrasound testing reveals that a fetus has microcephaly, that should also trigger Zika virus testing.

If a woman has a travel history but no symptoms of infection, an ultrasound should be done, Jamieson said. If it detects signs of microcephaly or brain abnormalities in the fetus, the woman should be tested for Zika virus infection.

If a pregnant woman tests positive for Zika virus infection, a series of ultrasounds should be considered, at three- to four-week intervals, to monitor the development of the fetus, the guidance suggests. It also recommends such women be referred to a maternal-fetal medicine or infectious disease specialist with expertise in pregnancy management.

“You do a referral so they’re being seen by the appropriate level of provider and deliver in an appropriate level of hospital,” Jamieson said.

There is no specific treatment for Zika infections. Pregnant women who test positive for the virus may use acetaminophen to lower their fevers.

They should not use aspirin or other non-steroidal anti-inflammatory drugs — which are not commonly used in pregnancy anyway — unless infection with dengue virus can be clearly ruled out. (Dengue infection can trigger internal bleeding, which these drugs could exacerbate.) Some tests cannot distinguish between Zika virus and dengue virus infection.

The possible link between Zika virus infection and babies born with microcephaly is still being explored. But evidence pointing to a link has been mounting.

Virus traces have been found in amniotic fluid taken during ultrasounds involving women shown to be carrying fetuses with the condition, in the brains of newborns with microcephaly who died, and in placenta tissue from women who miscarried fetuses with microcephaly.

Jamieson said the CDC cannot currently estimate how likely it is that a woman who was infected with Zika virus during pregnancy would give birth to a baby with microcephaly. 

“We know that microcephaly is still an uncommon occurrence, despite the fact that … there’s widespread Zika virus transmission in Brazil. But it’s still an unlikely outcome,” she said.

The CDC and the American College of Obstetricians and Gynecologists guidance released Tuesday includes a decision tree to help clinicians.

Zika virus chart
CDC

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