Ziika Forest

Tracing Spread of Zika Virus in the Americas

Posted on May 29th, 2018 by Dr. Francis Collins

A couple of summers ago, the threat of mosquito-borne Zika virus disease in tropical areas of the Americas caused major concern, and altered the travel plans of many. The concern was driven by reports of Zika-infected women giving birth to babies with small heads and incompletely developed brains (microcephaly), as well as other serious birth defects. So, with another summer vacation season now upon us, you might wonder what’s become of Zika.

While pregnant women and couples planning on having kids should still take extra precautions [1] when travelling outside the country, the near-term risk of disease outbreaks has largely subsided because so many folks living in affected areas have already been exposed to the virus and developed protective immunity. But the Zika virus—first identified in the Ziika Forest in Uganda in 1947—has by no means been eliminated, making it crucial to learn more about how it spreads to avert future outbreaks. It’s very likely we have not heard the last of Zika in the Western hemisphere.

Recently, an international research team, partly funded by NIH, used genomic tools to trace the spread of the Zika virus. Genomic analysis can be used to build a “family tree” of viral isolates, and such analysis suggests that the first Zika cases in Central America were reported about a year after the virus had actually arrived and begun to spread.

The Zika virus, having circulated for decades in Africa and Asia before sparking a major outbreak in French Polynesia in 2013, slipped undetected across the Pacific Ocean into Brazil early in 2014, as established in previous studies. The new work reveals that by that summer, the bug had already hopped unnoticed to Honduras, spreading rapidly to other Central American nations and Mexico—likely by late 2014 and into 2015 [2].

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