HealthPregnancy & Childbirth

Zika Virus: 5 Things We Know

Welcome to “This Week in Parenting Research”, a bimonthly column where I take a look at current research that may be of interest to parents. With Zika hitting the news again this week, I wanted to do a round up of the most current information about the transmission and risks, and what parents and expecting parents need to be aware of.

First, the basics: the Zika virus is carried by mosquitoes and currently endemic in about 45 countries. You are at risk for getting Zika if you have traveled to one of those countries and been bitten by a mosquito, or have had unprotected sex with someone who has been infected.

  1. Zika is mostly harmless for most people With Zika currently capturing headlines, I’ve seen a couple people get really confused or nervous about their own risk. It’s important to note that Zika is almost completely harmless for the vast majority of people who get it, with either mild symptoms similar to a cold or flu or entirely asymptomatic. There’s a suspicion it may trigger Guillain-Barre Syndrome in some people, but that link is still being investigated. Currently there don’t appear to be any deaths related to Zika. There’s no treatment or vaccine for Zika.
  2. Zika can be  harmful to fetuses. So if it’s not harmful to most people, why is it capturing headlines? Well, because despite not being that harmful to people in general, it appears to be linked to serious birth defects. The initial reports of Zika linked it to microcephaly, and it appears at least in Brazil the two are linked. However for reasons that remain unclear, Columbian officials have reported no such link but French Polynesian appears to have seen a link as well.  To be clear, the link appears to be related to active Zika infection during pregnancy, as birth defects seem to spike around 6-7 months after outbreaks are first reported. In the US, the CDC has created a registry for pregnant women with diagnosed Zika in order to track outcomes. They update every week here,, though they don’t give out details about individual cases. So far out of the 400 pregnancies being tracked, 13 have resulted in babies born with birth defects. Not all of these are microcephaly, and it appears Zika may be linked with other birth defects as well. The current CDC recommendations advise pregnant women to stay out of areas with a Zika outbreak, or if you do go to protect yourself.
  3. The exact risk is hazy. Unfortunately, researchers are still trying to figure out exactly how risky Zika is to fetuses, and when the risk is greatest. Currently it appears that it’s only those who contract Zika during their pregnancy that have a problem, but because so few people show symptoms it’s hard to tell how dangerous even that is. In a recent New England Journal of Medicine article, researchers created models using 10% infection rates and 80% infection rates to conclude the risk of defects after prenatal bought of Zika is somewhere between 1% and 13%. They also think the biggest risk is infection during the first trimester, but  found some risk in weeks 14-17. There’s a lot that goes in to proving causation for a public health risk, but so far the link appears to hold. Until more is known, the recommendations for pregnant women to avoid traveling to endemic areas or sex with a partner who has traveled to those areas is going to stay pretty broad.
  4. Zika has spread to the US in more ways than one Many of the pregnant women with Zika in the US traveled to other countries or had partners who did. Nearly every state has reported at least a few cases of Zika, almost all due to travel history. Last week there were a few cases discovered in Florida where no recent travel was found, which is why the CDC is suspecting the mosquitoes there are now transmitting the virus. The advice for pregnant women living in that area of Florida or who have traveled there since mid-June is to get tested for Zika in the first and second trimesters.
  5. You can subscribe to the CDC website to get updates To get updates from the CDC specifically about Zika, you can go to the main page here and sign up for updates. As the summer continues and more research is done, it is likely much of this information will change.  Hopefully the risks will be narrowed down a bit, and the testing for Zika will be improved.

If you’re looking for more details or background, the CDC webpage is always a good place to start, and the New York Times has a great quick Q&A here.

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Bethany is a perpetual student who just won't stop taking classes. She's gone from engineering to psych and family systems to applied statistics, and is really fascinated by how people feel about numbers. She blogs about this over at Graph Paper Diaries, and experimenting with contingency tables at Two Ways to Be Wrong.

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