RIO DE JANEIRO — The World Health Organization's top water expert said Friday the body "never advised against viral testing" for Rio de Janeiro's polluted waterways where about 1,400 athletes will compete in Olympic events next year.

Bruce Gordon, the WHO's coordinator of water, sanitation, hygiene and health, told The Associated Press in a phone interview from Geneva that testing for viruses "would be advisable" given it's known that human sewage pollution is rife in Rio's waters.

"WHO would support additional viral testing to further inform the risk assessment by authorities and to verify and address concerns raised by independent testing," Gordon said, indicating it was WHO's official stance. "In this case, measuring coliphages and enteric viruses would be advisable."

The comments come after Olympic Games Executive Director Christophe Dubi said earlier this week at a press conference in Rio that the International Olympic Committee ruled out viral testing because the WHO made it "very clear that bacterial testing is what should be followed."

The issue of more robust testing for Rio's waterways is in the spotlight following an independent, five-month AP analysis published July 30 of samples from each of the venues where athletes will have contact with water.

The results showed dangerously high levels of disease-causing viruses from human sewage at all water venues for next year's games, with an expert's risk assessment saying it was an almost certainty athletes would be infected by viruses, regardless of their sport, be it rowing, swimming or sailing. That doesn't automatically mean an athlete would fall ill — that depends on numerous factors, including their immune system.

The AP commissioned Brazilian virologist Fernando Spilki of Feevale University to test Rio's waters for three types of human adenovirus, as well as rotavirus, enterovirus and bacterial fecal coliforms. The viruses can cause stomach and respiratory ailments that would easily knock an athlete out of competition. The viruses can cause more serious, though rarer, ailments including heart and brain inflammation.

Brazil and nearly all nations rely on bacterial "markers" to determine the safety of recreational water. However, scientists have been pushing in recent years to include testing for specific disease-causing viruses in waters, as medical experts note that most waterborne illnesses are actually viral in nature.

"The WHO absolutely cares about viral pathogens," Gordon said. "Viral pathogens can absolutely be assumed to be in water that's impacted by sewage. We know it will be there."

He said that in Rio's waterways, "we know there is a problem."

"There is massive contamination and it's sad to see on the news," he said. "The WHO doesn't want to see people get sick, whether they're athletes or residents."

Gordon emphasized that standard bacterial testing should absolutely be done, and that the most important issue of all was not the monitoring but what Rio authorities would do to stop the massive flow of raw sewage into the city's waterways. For decades, the city has made little headway on building out a sewerage system, with the majority of the city's sewage not being treated.

Olympic officials didn't respond to emailed requests for comment, sent after hours at the IOC's Switzerland-based headquarters. Rio's local organizing committee said it stood by the IOC's comments earlier in the week.

This weekend, more than 330 sailors from over 50 nations will take to the waters of Rio's picturesque Guanabara Bay, competing in an Olympic sailing test event.

Many of the boats will be launched from a small beach where the AP's testing found human adenovirus levels 127,000 times what experts would consider highly alarming on a southern California beach.

AP Sports Writer Stephen Wade contributed to this report.

See the summary findings and methodology of the AP's study:

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