Written by Joe Ballenger

An important paper came out in the journal Science, which I think is a great update of the Zika virus situation in Brazil. Here are the highlights:

Microcephaly and Zika

• The correlation between Zika cases and microcephaly, when measured in relation to live births is weak, but statistically significant.
• Overdiagnosis due to increased reporting and inconsistent definitions of microcephaly are still very important factors that could skew results.
• Zika virus appears to be transmitted between mother and fetus
• Cell culture studies show that Zika infects and kills cells that will differentiate into neurons, although animal studies still need to show that Zika can cause microcephaly.
• These results still only demonstrate correlation, and do not demonstrate causation.
• Although the virus is evolving, there is no evidence that any genetic change has led to increased virulence or pathogenicity. The changes so far all look like so-called silent mutations.

Zika Introduction to Brazil

• The strain of Zika virus circulating in Brazil is related to the strain which was responsible for the outbreak in French Polynesia
• The viruses all form one cluster, which implies a single introduction. However, multiple introductions still can’t be ruled out.
• Three hypothesis remain about potential introduction sources. The most likely point of introduction was the 2013 Confederations Cup soccer tournament, which had competitors from French Polynesia. However, this doesn’t match up with the French Polynesia outbreak timeline.

The Bottom Line

I’m still following the Zika outbreak, but I’m trying to be very careful with what I post. There’s a lot of rumors going around, and I really don’t want to spread wrong information. So updates will come, but will be very infrequent.

Science takes time, and it’s imperative that it’s done *right* even if it’s not done fast. Our knowledge of the situation is evolving, but these studies don’t come nearly as quick as we’d like to see. That’s the nature of science, though…things are always slow.

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