Organizers for the 2016 Summer Olympics will reportedly administer viral tests to the water in Rio de Janeiro to determine whether it will be suitable for competitions, per Rob Harris of the Associated Press (via ABCNews.com).
The AP (via the New York Times) conducted an investigation into the matter and reported on its results in July. The news organization "found dangerously high levels of viruses and bacteria from sewage at the sites for the 2016 Olympic and Paralympic water sports."
The source of the issue is runoff from streams around Rio that contain sewage and any other waste from the city.