Health experts are concerned about the 2016 Summer Olympics in Rio de Janiero, Brazil, after water tests have revealed that super-high levels of bacteria and viruses continue to thrive within the city’s aquatic competition venues, The Associated Press reports.

According to a recent AP analysis of water quality taken over five months in the South American city, disease-causing contaminants at several sites are measuring up to 1.7 million times higher than what’s considered “hazardous” at most U.S. beaches.

Tests show that many, if not all, of the swimming, canoeing and sailing sites designated for the games are rife with untreated human feces and garbage—which could put athletes at risk for a wide array of health problems, including infectious diarrhea, hepatitis A virus (HAV), gastroenteritis, and several types of enteroviruses, among others.

Rio’s government insists it has already begun several projects that hope to clean up the waters before game-time—like plans to treat up to 80 percent of sewage feeding into city waters, as well as creating new eco-barriers and eco-boats to hold back mess. However, activists and athletes alike are pretty skeptical of what cleanup crews will be able to achieve in one year. Many are afraid they could become too sick to compete.

Representatives from the International Olympic Committee (IOC) are still saying everything is fine. “The Rio authorities are following WHO [World Health Organization] testing standards and according to the WHO there is no significant risk to athletes,” they wrote in a statement responding to the AP report, noting that international standards only have to test for bacterial—not viral—pathogens.

As of now, the U.S. Centers for Disease Control and Prevention (CDC) is strongly recommending that all athletes and travelers to Brazil get vaccinated for hep A and typhoid, which are both spread by contaminated food and water.

The AP, the WHO and the IOC will continue to regularly check the waters in Rio for dangerous contaminants leading up to the games.