Study: Zika landed in Brazil 2 years before it was detected

The researchers coupled cutting-edge genetic sequencing of the virus with an analysis of human travel patterns.

The sequence information may also help in future understanding of how the virus causes disease, Lipkin said.

[...] it remains a mystery why the virus is increasingly linked to serious birth defects and other health problems, he added.

A good bet is the virus landed in June 2013 in the city of Recife, around the time of the 2013 Confederations Cup soccer tournament in Brazil, said one of the study's lead authors, Dr. Pedro Fernando da Costa Vasconcelos of Brazil's Health Ministry.

Or perhaps the virus was introduced to Brazil and French Polynesia at about the same time — carried by people from some third location, said the University of Oxford's Oliver Pybus, another study co-author, in an email.

[...] on Thursday, U.S. health officials said 273 lab-confirmed Zika infections have been reported in the 50 states in the last year — a count that includes 19 pregnant women.