"The Brazilian strain of Zika virus harms health in ways that science has not observed before", the letter said. "An unnecessary risk is posed when 500,000 foreign tourists from all countries attend the Rio Olympics, potentially acquire that strain, and return home to places where it can become endemic".
The letter called on the WHO to convene an independent group to advise it and the International Olympic Committee with a priority for science and public health, as well as the spirit of sport. Brazil has been the hardest-hit of the approximately 60 nations that have reported Zika outbreaks - and has by far the most cases of brain-damaged babies linked to the virus, almost 1,500.
The World Health Organization's chief says she will convene an expert committee to consider whether the Rio de Janeiro Summer Olympics should proceed as planned, following concerns raised about the threat of the Zika virus. The US Centers for Disease Control and Prevention concluded after months of research that infection with Zika in pregnant women is a cause of the birth defect microcephaly, where infants are born with abnormally small heads, and other severe brain abnormalities in babies.