The U.N. health agency says reports from national authorities indicate no confirmed laboratory cases of the Zika virus in anyone associated with the Rio Olympics.

Up to 37 athletes, tourists and journalists travelling to Brazil for the Summer Olympics will bring Zika virus back to their home countries in a “worst-case scenario,” scientists say in a new study

The upcoming Olympic games are not likely to have a major impact on the spread of Zika virus, although four developing countries could face a substantially higher risk.