Zika genomes provide clues to virus’ introduction to Brazil

Using genome sequences for a handful of Zika viruses (ZIKV), an international team estimates that the virus made its way to Brazil sometime in 2013, potentially piggybacking with travelers from affected areas in the Pacific Islands. As they reported online in Science, the researchers sequenced seven ZIKV genomes isolated from infected individuals in Brazil, including an infected newborn with microcephaly. Using phylogenetic information gleaned from the sequences, together with phylogenetic clues, they estimated that ZIKV was introduced to Brazil once between May and December 2013 — a time period that overlaps with an uptick in air travel from ZIKV endemic regions, according to airline flight data tapped for the analysis. Co-senior author Pedro Fernando da Costa Vasconcelos, an infectious diseases and virology researcher with the Brazil Ministry of Health’s Evandro Chagas Institute, explained that this earlier-than-anticipated introduction may help to explain the apparent explosiveness of the 2015 outbreak. “It had at least a...