There seems to be growing evidence that a recently spreading strain of Zika virus is in fact linked to microencephaly and other birth defects in newborns (see here, here, and here for examples).

I understand that this is currently an active area of research and a number of questions remain unanswered. However, even given the current uncertainties, I feel any discussion about when a mother gets infected has been largely ignored by all of the news/media/science outlets I've seen.

My question is: does the virus lead to birth defects only if the mother gets infected during pregnancy, or can a previous (or latent) infection lead to similar birth defects? If the former, does timing of infection during different trimesters matter?


1 Answer 1


As you mentioned, there is evidence that mother-child transmission of Zika virus causes congenital anomalies like microencephaly.
Now your question, if a cleared infection before the pregnancy could affect it? In principle, no. Once the virus is cleared, it should not reactivate, unless there is reinfection. Here's a quote from the Zika article from Uptodate.com:

Women of childbearing potential — It is uncertain how long women of childbearing potential should wait between Zika virus exposure/infection and conception. Most pregnant women with Zika virus exposure give birth to normal infants [111]. Zika virus usually remains in the blood of an infected person for a few days to a week, and thus far there is no evidence that a fetus conceived after the virus has cleared from the blood would be at risk for Zika infection [94,112]. However, information regarding the persistence of Zika virus following infection is not known. It has been suggested that infection due to other flaviviruses such as West Nile virus may persist years after initial infection [113-115]; these data are controversial. Pending further study, healthcare providers should encourage women to make such decisions based on their individual circumstances, values, and preferences.

Daniel J Sexton, MD Editor-in-Chief — Infectious Diseases Section
Editor — Bacterial Infections
Professor of Medicine
Duke University Medical Center

  • 1
    $\begingroup$ Citing whole sections is discouraged. $\endgroup$
    – AliceD
    Mar 12, 2016 at 6:36
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    $\begingroup$ @Christiaan Except all of it is relevant, and answers directly the question $\endgroup$
    – Maljam
    Mar 12, 2016 at 6:43
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    $\begingroup$ There are citations to unmentioned sources and its better to synthesize an answer rather than reproducing it. The info is good, it's just the way it's presented. $\endgroup$
    – AliceD
    Mar 12, 2016 at 6:50
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    $\begingroup$ Could you also provide a link to the article and expand on points it makes $\endgroup$
    – rg255
    Mar 12, 2016 at 7:58
  • $\begingroup$ @rg255 I would like to, but the article is not accessible for free, I can only access it because of my University affiliation. But here's the link: uptodate.com/contents/zika-virus-infection $\endgroup$
    – Maljam
    Mar 13, 2016 at 2:36

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