AUDIE CORNISH, HOST:
There's now evidence that the Zika virus was spreading through South America long before health officials detected it last year. The finding suggests Zika could be hiding out in other corners of the world. NPR's Michaeleen Doucleff reports.
MICHAELEEN DOUCLEFF, BYLINE: Oliver Pybus studies viruses at the University of Oxford. He says hidden inside Zika's genes are clues about the outbreak in Latin America.
OLIVER PYBUS: Where the outbreak has come from, when it first arrived and how it's been spreading.
DOUCLEFF: So he and an international team of scientists decoded the genomes of Zika viruses found in patients in Brazil. The pattern in the genes suggest that one person, possibly from French Polynesia, introduced Zika to the Americas, but the genomes also told them something else.
PYBUS: We were able to use a technique called the molecular clock to extrapolate backwards in time and estimate when that introduction might've occurred.
DOUCLEFF: The time they came up with, late 2013. That means Zika was infecting people more than a year before Brazil reported its first cases. Duane Gubler is an emerging disease expert at Duke-NUS Medical School in Singapore. He says this is typical of mosquito-borne viruses like Zika.
DUANE GUBLER: They're frequently introduced into areas long before the epidemic is recognized.
DOUCLEFF: Which means, Gubler says, any country with the right mosquitoes could have Zika spreading in its population right now without anyone knowing it. Gubler says countries in Southeast Asia are particularly at risk. Several countries there have a sprinkling of Zika cases each year, and this new research out this week in the journal Science suggests that there's probably more.
GUBLER: We've tried to alert the countries to intensify surveillance for Zika for that very purpose.
DOUCLEFF: Gubler think it's just a matter of time before a big outbreak erupts there in Southeast Asia. Michaeleen Doucleff, NPR News. Transcript provided by NPR, Copyright NPR.
