(HealthDay News) – The Zika virus likely arrived in the Americas between May and December 2013, more than a year before it was first reported in Brazil, according to a study published in Science.

Researchers utilized next generation sequencing to generate 7 Brazilian Zika virus genomes, sampled from 4 self-limited cases, 1 blood donor, 1 fatal adult case, and 1 newborn with microcephaly and congenital malformations. Phylogenetic and molecular clock analyses demonstrated a single introduction of the Zika virus into the Americas between May and December of 2013. The estimated date corresponds with a period when there were increased numbers of air travelers to Brazil from countries where Zika was known to be present, and when there were Zika outbreaks in the Pacific Islands.

Zika was detected in Brazil in May 2015. Cases of microcephaly potentially associated with Zika infection were identified in November 2015.

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“Though the sample size used in this study is small…the work represents an important result given how little is known about this emerging virus to date,” researchers led by Nuno Rodriguez Faria, PhD, explained in a news release from the American Association for the Advancement of Science. Faria is with the Ministry of Health in Ananindeua, Brazil.


  1. Faria NR, da Silva Azavedo RS, Kraemer MUG, et al. Zika virus in the Americas: Early epidemiological and genetic findings. Science. 2016; doi:10.1126/science.aaf5036.