No plans to move Rio Olympics, Brazil officials say

In a statement, the nation's health ministry said it would continue to follow the guidance of the World Health Organization (WHO), which has deemed the risk of Zika infection in the month of August -- the middle of winter in Brazil -- to be "minimal."

Officials with Rio's Olympic organizing committee, meanwhile, were quoted Saturday by the O Globo newspaper as saying that the Games would continue on track.

Friday's letter from 150 doctors, scientists and researchers disagreed with that assessment, warning that it would be "irresponsible" and "unethical" to hold the Games in Rio, the second most affected city in Brazil by the Zika crisis.

"Our greater concern is for global health. The Brazilian strain of Zika virus harms health in ways that science has not observed before," said the letter, signed by experts in the United States, Britain, Canada, Norway, the Philippines, Japan, Brazil, South Africa, Turkey and Lebanon, among others.

Zika can cause birth defects, including a devastating syndrome known as microcephaly in which babies are born with unusually small heads and brains.

Nearly 1,300 babies have been born in Brazil with the irreversible defect since the mosquito-borne Zika began circulating there last year.

While saying it is safe for most people attending the Olympic Games, the WHO earlier this month urged those traveling to Brazil to take precautions against mosquito bites. The organization has said pregnant women should avoid areas where Zika is circulating, including Rio de Janeiro.