Pollution has become a major concern at venues for many of the water-based sports, including the Lagoa Rodrigo de Freitas where rowing and canoe sprint are due take place, Copacabana Bay where triathlon and open water swimming will be held, and the sailing venue on Guanabara Bay.

The sailing venue has attracted most concern, with anstudy conducted earlier this year by Associated Press reporting a "major risk" of athletes contracting illnesses, with at least two sailors having been taken ill during August's test event.

Unlike investigations carried out by Rio 2016, which have relied upon bacterial testing, this investigation was based on viral testing, prompting calls for organisers to follow suit. 

The WHO have now recommended not using virus testing for routine monitoring, despite previously suggesting it could be neccessary.

They now claim "there are no standardised methods for it, making the interpretation of results difficult".

Rio 2016’s executive director of communication Mario Andrada said: “Tests for viruses will not be conducted because the WHO does not see the need.

In “specific exceptional circumstances” they could still be used, however, such as an outbreak of a disease that may have a viral cause, or as part of a research protocol.

Numbers of tests focusing on two types of bacteria - enterococci and E.coli -  will be increased from their current weekly basis to every three days, and eventually on a daily basis, it was revealed.

Tests use standard indicators, based on international water monitoring guidelines in the context of public health.

Most of the health problems, the WHO, claim are related to contaminated faeces in the water, and, if ingested, are limited to short-term gastroenteritis, such as what affected 15 members of the United States rowing team following their test event earlier this summer.

The issue, nevertheless, remains a major challenge with less than 10 months to go until the Opening Ceremony.

Using the Games as a catalyst to clean the waters was a key pledge by Rio when bidding for the Games against Chicago, Madrid and Tokyo in 2009.

International Sailing Federation chief executive Peter Sowrey has warned the event could be moved further out into the Atlantic in order to ensure cleaner water, but subsequent messages from the governing body have been more supportive.

Due to a feeling by some that viral testing was a more accurate way of assessing the risk of illness, however, Brazilian officials and the WHO could face the risk of severe criticism if there is now a spate of problems during the Games.

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