Doug Stanglin

USA TODAY

The World Health Organization, which in February declared the spread of Zika in the Americas a global emergency, said Saturday there is "no public health justification" for postponing the 2016 Olympic Games in Rio de Janeiro.

The statement by the Geneva-based U.N. health agency comes one day after a group of doctors, scientists and bioethicists wrote a letter to the organization calling for the Aug. 5-21 Games to be postponed or moved because of concerns of the spread of Zika.

Friday’s letter cited recent scientific evidence that the mosquito-borne virus causes severe birth defects, most notably microcephaly, in which babies are born with abnormally small heads and incomplete brain development. In adults, it can cause neurological problems, including a rare syndrome that can be fatal or result in temporary paralysis.

The Zika outbreak began in Brazil a year ago. Between February and April 2016, Brazil's health ministry registered 91,387 likely cases of the virus, Reuters reports.

The ministry said the number of confirmed cases of microcephaly dropped to 1,326 in the week through May 7 as doctors and Brazilian health officials found some suspected cases were not the disorder. Suspected ones under investigation continued to decline to 3,433.

The WHO statement made no direct reference to Friday’s letter, which also alluded to what it called an “overly close” relationship between the health agency and the International Olympic Committee.

WHO, however, noted Brazil is one of almost 60 countries and territories reporting the transmission of the Zika virus by mosquitoes. "People continue to travel between these countries and territories for a variety of reasons," WHO said. "The best way to reduce risk of disease is to follow public health travel advice."

Based on the current assessment of the virus worldwide, WHO said, "there is no public health justification for postponing or canceling the Games." The agency said it would continue to monitor the situation and "update our advice as necessary.”

The organization recommended visitors to the Games use insect repellents and wear clothing that covers as much of the body as possible. It also recommended travelers "practice safer sex," including the use of condoms, or abstain from sex during their stay in Brazil and for at least four weeks after their return because the virus can be transmitted through semen.

The letter calling for a postponement or cancellation of the 2016 Games cited the possibility of travelers acquiring Zika in Rio and then returning home, especially to areas currently unaffected by the virus.

The virus doesn't spread from person to person like the flu. If a mosquito bites an infected person, it then can pass on Zika to the next person it bites. The virus can also be transmitted through sex and blood transfusions.

The authors also noted that despite increased efforts to wipe out the mosquitoes that spread Zika, the number of infections in Rio went up rather than down.

“It is unethical to run the risk, just for Games that could proceed anyway, if postponed and/or moved,” the letter stated.

The letter writers included Amir Attaran, a University of Ottawa professor who specializes in public health. It was co-authored by Dr. Arthur Caplan, the director of the division of medical ethics at New York University, as well as by NYU professor Lee Ingel and Christopher Gaffney from the University of Zurich.