Zika has faded from the headlines like a mosquito’s dying buzz.
But the risk the insidious pathogen poses to a pregnancy hasn’t gone away, and public health authorities are grappling with how to get the message out to pregnant women. Despite public confusion over whether Zika remains a public health threat, the Centers for Disease Control and Prevention continues to warn women who are pregnant to avoid traveling to wide swathes of Latin America and the Caribbean.
“People are just going to have to accept that as part of the new reality,” Dr. Martin Cetron, director of the CDC’s global migration and quarantine division, told STAT in an interview. “Until we have better prevention tools, we’re just facing this as part of the new normal.”
“If this were my daughter, I would want her to know and I would caution her not to go there at this time. And that’s tough medicine. I understand that.”
For most people, Zika infection is mild, if that. It’s believed that as many as 4 of 5 who are infected don’t experience any symptoms.
But infection in pregnancy carries a life-altering risk to the developing fetus. The virus is neurotropic — it gravitates to and attacks key cells in the developing central nervous system. Microcephaly — an abnormally small head and often an underdeveloped brain — is the most obvious of Zika’s harms. But a range of defects including brain tissue destruction as well as visual and hearing deficits are seen in babies born after prenatal infection.
Some of the defects are profound and are not problems these children will outgrow. And the risk is not small. New data on Zika-infected pregnant women from the U.S. territories found 5 percent of those pregnancies were affected.
Researchers studying the virus fear other, more subtle problems will only become apparent as children infected in the womb start lagging, developmentally, behind their peers.
Public health officials have been desperate to try to prevent these kinds of birth outcomes since Zika’s link to birth defects was first recognized. And that hasn’t changed as the public’s sense of alarm over the Zika outbreak has subsided.
But officials know they’re up against a challenge in trying to keep this issue on the radar of the people who need to pay attention.
“Last year, health experts were concerned that the media overstating the threat from Zika would make ongoing messaging to manage the actual level of risk more difficult. That’s where we are now,” said Sandra Mullin, a senior vice president of Vital Strategies, a nonprofit that provides public health expertise to low- and middle-income countries.
“Zika, West Nile virus, and other mosquito-borne diseases that once seemed urgent and novel and captured the attention of the news media and policymakers now face the fatigue of other chronic conditions and diseases that present similar challenges for public health communicators.”
Cetron said if peak transmission in a place has passed but some low level spread of the virus remains, the risk of contracting Zika may be low. But with such devastating consequences, the CDC isn’t thinking about downgrading its warnings.
“Even a low level risk, especially for something which is often difficult to recognize, may constitute a really serious public health outcome for this narrow segment of the population.”
The World Health Organization concurs.
“It’s a tricky one, this,” Dr. Anthony Costello, WHO’s director of maternal, child, and adolescent health said of Zika, the only known mosquito-transmitted virus to cause birth defects.
That’s an understatement. The WHO tries to quantify the Zika risk by grouping countries and territories as follows: those where spread is new and where there is ongoing transmission; those where the virus has circulated for a while and hasn’t stopped; those where transmission appears to have stopped but could resume; and those where the conditions for spread exist — in other words, the right mosquitoes — but the virus hasn’t been found.
There are 148 locations on the list. The first two categories, which pose the highest risk, include 58 and 20 countries and territories, respectively.
“Obviously with pregnancy, you’re going to take extra caution. And if people don’t need to travel [there], the advice to be absolutely cautious would be not to,” Costello said.
Likewise, advice to people of child-bearing age isn’t changing either, he said. The WHO recommends couples who have been to places where they might have contracted Zika wait six months before trying to conceive.
Cetron said the CDC’s travel advice, found in its regularly updated Yellow Book or in the location-specific advice it lists on its website, sometimes urges pregnant women to take special care. For instance, the agency cautions pregnant women against traveling to places where they can contract malaria, because it can be more dangerous during pregnancy.
That’s the way Zika will likely be handled going forward, Cetron said. It has become another one of the things pregnant women have to guard against.
“Many pregnant women won’t like giving up alcohol for nine months of pregnancy or other kinds of accommodations pregnant women make on behalf of their unborn child in order to get a healthy start,” he said.
“I think it’s difficult, but I don’t think it’s unreasonable. I wish it were different.”
An earlier version of this story incorrectly identified Sandra Mullin as a consultant.