RIO DE JANEIRO (AP) — A timeline of key moments since The Associated Press first reported on contamination of Rio de Janeiro's Olympic waterways:

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July 30 — The Associated Press publishes its first story based on data from five months of viral and bacterial testing of Rio's venues for Olympic water sports. The levels of disease-causing viruses were similar to those found in raw sewage. The medical director of the International Olympic Committee says in response that there are no plans to change venues and that the World Health Organization, which acts in an advisory role for the IOC, has reassured Olympic officials there is "no significant risk of athlete health."

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July 31 — The Rio de Janeiro state government and the state environmental agency blast the AP report as alarmist and say it is unfair to judge Rio's waters based on viral counts, limits of which are not designated in Brazilian legislation — or most nations. They also question the qualifications of the laboratory where the AP samples were analyzed. David Zee, an oceanography professor at Rio's state university who has studied pollution in Guanabara Bay for decades and had no part in the AP study, says: "It's natural that the authorities react saying that 'everything is fine,' but everything is not fine." He says the AP testing "was done in a trustworthy lab."

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Aug. 1 — WHO tells the AP in an emailed statement that it has now "advised the IOC to widen the scientific base of indicators to include viruses. The risk assessment should be revised accordingly, pending the results of further analysis." The International Sailing Federation becomes the first to break with the IOC, saying it will carry out its own viral testing of Rio's waters.

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Aug. 2 — IOC reverses course. "The WHO is saying they are recommending viral testing," IOC's medical director, Dr. Richard Budgett, tells the AP. "We've always said we will follow the expert advice, so we will now be asking the appropriate authorities in Rio to follow the expert advice, which is for viral testing."

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Aug. 4 — Matt Smith, head of World Rowing, says that "together with the WHO and the IOC, we're going to follow what they say. We will ask that viral testing is done. If there is a problem, we will react. It's our moral duty."

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Aug. 10 — WHO changes direction, telling the AP in an email that it "will not issue an 'official recommendation' on viral testing." It says that "viral testing would not help significantly in the measurement and assessment of water quality." This statement contradicts WHO's own published studies showing little to no correlation between the levels of bacterial and viral markers in water — meaning that just testing for bacteria alone tells experts little about the amount of disease-causing viruses in recreational waters. Also on this day, the AP learns 13 American rowers became sick with stomach illness at the World Junior Rowing Championship held the previous four days.

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Aug. 12 — IOC rules out viral testing of Rio's waters. Olympic Games Executive Director Christophe Dubi says IOC will be sticking to WHO guidelines recommending only bacterial testing. "WHO is very clear that bacterial testing is what should be followed," Dubi says at a news conference in Rio.

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Aug. 14 — WHO again reverses course. In a telephone interview with the AP, Bruce Gordon, WHO's top water safety expert, says that while bacterial testing is the global standard, "WHO would support additional viral testing to further inform the risk assessment by authorities and to verify and address concerns raised by independent testing. In this case, measuring coliphages and enteric viruses would be advisable."

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Aug. 15 — International Sailing Federation changes its stance. Dr. Nebojsa Nikolic, the federation's top medical official, tells the AP that "we will certainly not" do viral testing.

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Sept. 1 — Carlos Nuzman, head of Rio's local Olympic organizing committee, tells the AP in an interview that "we will do" viral tests and says work is already underway to understand how best to carry out the viral analysis.

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Sept. 16 — The international swimming federation calls for Olympic officials to carry out viral testing in Rio, according to an internal document obtained by the AP. The federation "and its Sports Medicine Committee strongly recommend that viral tests should also be performed," it says in a letter to Olympic organizers.

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Oct. 16 — WHO again changes course, issuing a statement saying it recommends only bacterial testing for Rio's Olympics. It says there is "a lack of standardized methods and difficulty interpreting results" for routine testing of viruses. Mario Andrada, spokesman for Rio's Olympic organizing committee, says they consider that to be "the final instructions for Rio 2016" and that viral testing will not be done.

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Oct. 24 — WHO, in an emailed statement, says its comment "not recommending 'routine' viral testing is not analogous to WHO recommending that Brazil do nothing and that WHO is unconcerned with viral pathogens in water. ... In fact, we have experts engaged on examining the best monitoring protocols and we will be discussing virus testing at an upcoming meeting in Brazil."

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Online:

Interactive, summary findings and methodology of AP's study: http://interactives.ap.org/2015/brazil-water/