Tests conducted over a five-month period found that the waters of Rio de Janeiro, the venue for the 2016 Summer Olympics, are “rife with human sewage” and sickening sailors who are training there.

The testing, commissioned by the Associated Press, revealed dangerously high levels of viruses and bacteria from sewage where the athletes will compete in water sports. However, an Olympic official said last week that there are no plans to monitor the water for viruses, which many experts consider the biggest problem.

“This is by far the worst water quality we’ve ever seen in our sailing careers,” Ivan Bulaja, a coach for the Austrian team, which has spent months training on the Guanabara Bay, told the Associated Press. “I am quite sure if you swim in this water and it goes into your mouth or nose that quite a lot of bad things are coming inside your body.”

The AP conducted four rounds of tests, starting last March. The results have alarmed experts and dismayed competitors training in Rio, some of whom have become ill with fevers, vomiting and diarrhea.

The Rio de Janeiro state environmental agency released a statement last week questioning the AP’s testing and accused virologist Fernando Spilki, who carried out the testing, and his university of “seeking notoriety.”

Mario Moscatelli, a biologist who has spent 20 years lobbying for the cleanup of Rio’s waterways, said the state environmental agency was trying to divert attention from the pollution problem.