ROBERT SIEGEL, HOST:
The Zika epidemic is scary. The mosquito-borne virus is linked to birth defects in Brazil, and there are concerns that it's spreading. And in our coverage, this question has come up. In Brazil right now, how many known cases are there of Zika-related microcephaly? That's where an infant is born with a small head and with brain damage. NPR's Lourdes Garcia-Navarro in Rio de Janeiro went looking for an answer.
LOURDES GARCIA-NAVARRO, BYLINE: Brazil's Ministry of Health gives updates every week. The number that gets the most publicity is reported cases of microcephaly. By reported, that means hospitals have alerted the Ministry of Health that they have a suspected case of Zika-related microcephaly. That number has been going up. Last week, it was at 4,180. But after a case has been reported, it gets investigated. Microcephaly can be caused by many things, and the authorities have found 462 cases that are either not microcephaly or it's a type of microcephaly that has been caused by something else - an infection like rubella or genetic abnormalities. Dr. Manoel Barral is the Bahia director of the Oswaldo Cruz Foundation, one of the premier research facilities in Brazil.
MANOEL BARRAL: The numbers seem messy, but they are really more cautious - I mean, not to attribute to Zika things that we cannot be sure are related to Zika.
GARCIA-NAVARRO: Only six cases so far have been linked with certainty to the Zica virus. He says that's not unusual. At the moment, you can only test positive for the virus if you have an active infection, which normally only lasts for a short period of time. So the cases that have either been confirmed or are under investigation as being Zika-related as of this moment in Brazil is 3,718. Lourdes Garcia-Navarro, NPR News, Rio de Janeiro.