I just read a fascinating paper on Zika. A note: the paper involves termination of a pregnancy, so I don’t recommend reading if you’re sensitive to that topic.

Second note: it also involves discussion of a subsequent postmortem.

It’s a case study (so you know, general disclaimer that we’re looking at an n of 1) of a Finnish woman who traveled to Mexico, Guatemala, and Belize at 11 weeks pregnant back in November. She contracted Zika, which she started showing signs of once she was back home in the US. Later on, her fetus started showing serious brain abnormalities (atrophy in the cerebral mantle and a small corpus callosum for its age - though it didn’t meet the criteria for microcephaly), and she chose to terminate at 21 weeks.

The fascinating bit is in what they found by conducting a postmortem of the fetus. It had very high concentrations of the virus in the brain, placenta, fetal membranes, and umbilical cord. The mother, just before the termination, was showing low viral loads, and a week afterwards showed none.

What we know about Zika from the research that’s previously been done is that non-pregnant, healthy people tend to fully kill off the virus about a week after onset of infection. This pregnant woman still had viral RNA in her system 10 weeks after infection, but killed it off after termination of pregnancy. It seems that in pregnant women, the virus finds the fetus to be a prime location for replication and immune evasion. It lasts beyond the time frame that it would normally last in a non-pregnant individual.

Beyond that, the case study also provided some interesting histopathological results that I’m guessing this group will be less interested in (such as abundant apoptosis of intermediately differentiated postmigratory neurons), but suffice to say the data may provide a better understanding of how the virus is causing damage to fetal brain tissue. The paper’s authors also recommend more detailed fetal scans for Zika pregnancies, as initial scans did not show the problem in this case for many weeks after infection.

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I’ll try to link the pdf if anyone is interested in more details, but I’m not positive the link will work for everyone. It’s a brand new paper (published March 30, 2016) in the New England Journal of Medicine by Driggers et al.: Zika Virus Infection with Prolonged Maternal Viremia and Fetal Brain Abnormalities.

http://www.nejm.org/doi/pdf/10.105…

Some of you may recall that I previously posted about a paper speculating that the microcephaly increase might only be indirectly related to Zika via mosquito larvicides being widely used in Brazil. Evidence definitely seems to now point to a direct linkage between Zika and issues with fetal brain development. (Though I still think Brazil’s widespread use of larvicides in drinking water is a very bad idea.)