No one got Zika at the Olympics in Rio de Janeiro despite major concerns from experts that the games would exacerbate the spread of the illness.

The World Health Organization said Thursday that so far there have been "no laboratory confirmed cases of Zika virus in spectators, athletes or anyone associated with the Olympics." The agency said some cases could still occur, especially given the one-week incubation period of the virus.

The two-week Olympics concluded on Aug. 21 in Rio.

The latest Zika outbreak, which has spread to more than 50 countries and territories, began in Brazil last year.

However, the WHO decided against pushing for delaying or canceling the Olympic games because they took place during Brazil's winter and mosquito populations are down. Rio officials also increased spraying to kill mosquitoes in areas around the Olympic venues.

A group of more than 100 scientists wrote to the WHO in May to either move or cancel the Olympics due to the threat of Zika, which causes a mild illness and a birth defect called microcephaly.

"An unnecessary risk is posed when 500,000 foreign tourists from all countries attend the games, potentially acquire that strain, and return home to places where it can become endemic," the letter said.

One expert who called for the Olympics to be postponed isn't buying the WHO's statistics.

"There have been new cases reported in Rio during the Olympics," said Amir Attaran, a public health professor at the University of Ottawa. "Since obviously Brazil's standard epidemiological reporting system is not set up to distinguish between those who attended the Olympics and those who did not, any more than those who prefer Coke over Pepsi."