Zika virus likely present in Americas long before 2015-16 epidemic

The Zika virus circulated in many regions of the Americas for months before cases were detected, according to a study from an international research team from the Broad Institute of MIT and Harvard and collaborating institutions. Lead author was Pardis Sabeti, professor of immunology and infectious diseases at Harvard T.H. Chan School of Public Health and a Broad Institute Member.

The study was published May 24, 2017 in Nature.

The analysis of 174 Zika virus genomes — the largest collection of Zika genomes to date —revealed the trajectory and evolution of the virus as it spread throughout the Americas. The genomes were sequenced from patient and mosquito samples collected in 11 affected countries and territories, allowing the researchers to reconstruct for the first time the spread of the virus across South and Central America, the Caribbean, and into the southern United States.

The findings suggested that Zika was circulating in Brazil around February 2014, a year before that nation’s first confirmed infections were reported. Similarly, the virus appears to have arrived in Colombia, Honduras, Puerto Rico, and elsewhere in the Caribbean from 4.5 to 9 months before the first confirmed local infections.

“Our data and findings will support development of more effective molecular diagnostic tests, as well as improved public health surveillance tools,” said study co-first author Hayden Metsky, a graduate student in the Sabeti lab.

The study was published with a companion paper from the [[Scripps Research Institute and colleagues examining Zika’s introduction into Florida, and another study by researchers at the University of Oxford and colleagues examining the virus’s establishment and early spread within and beyond northeastern Brazil.

See the Broad Institute press release, maps, and video: Zika virus likely circulated in the Americas long before its detection during the 2015-16 epidemic

Read a May 24, 2017 NBC News article on the studies: Zika Virus Was Spreading Quietly a Year Before Anyone Knew, Gene Study Shows

Learn more

Tracking a duo of deadly diseases (Harvard Chan news interview with Pardis Sabeti)

Zika in the news (Harvard Chan School news)

The Zika Crisis: Latest Findings (Harvard Chan School Forum)