An initial report suggests that the cause of athletes falling ill following a Sunderland triathlon was norovirus, rather than E. coli.  

The Sunderland leg of the World Triathlon Championships has been plagued with scandal after 88 world-class athletes reported diarrhoea and/or vomiting following the race.

After the event, Environment Agency tests emerged showing that E. coli levels in water near the swim course at Roker Beach, in Sunderland, were at 3900 E. coli bacteria colonies per 100ml. This is over 39 times higher than typical readings taken in the previous month, prompting concerns over the safety of the event and beach at large.

But an investigation by the UK Health Security Agency (UKHSA) has found that norovirus is present in 60 per cent of stool samples submitted by athletes, making it “the most likely explanation” of the mass sickness. 

Read more: Investigation into Sunderland's water quality blocked

UKSEA has tested 31 faecal samples from athletes for a range of viral and bacterial pathogens that can cause symptoms of diarrhoea and vomiting.

So far, lab results indicate that 60 per cent of samples have evidence of norovirus infection. The remaining samples either tested negative or were positive for other infections including sapovirus, astrovirus and rotavirus.

To date, no UKSHA tests have turned up evidence of E. coli cultures that cause gastrointestinal illness, although other, more harmless strains of the E. coli bacteria were found in four stool samples.

The UKHSA report said: “People can naturally carry organisms in their gut, and so it would not be possible to say whether they had a positive result due to their participation in the event or that they were already carrying these organisms.

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“It is not uncommon to detect more than one infection following testing of faecal samples, but the predominance of Norovirus makes it the most likely explanation of illness in participants.”

Norovirus is very easily transmitted through contact with people with the infection and any food, water, surfaces or objects that have been contaminated with the virus. Although investigations continue, the exact source of the infections may not be possible to determine.

Dr Kirsty Foster, Consultant in Health Protection said: “We thank everyone who took the time to contact British Triathlon to undertake sampling and respond to our epidemiological investigations and I hope that today’s preliminary findings will offer some reassurance.

“Norovirus is a very unpleasant stomach bug but tends to pass after a few days with most people usually making a complete recovery without any specific treatment. Rest and drinking lots of fluids are important to avoid dehydration. Norovirus can easily spread from person to person, particularly in large groups.

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“The risk to the wider public remains very low. However, it is always important that we all follow advice on how to manage symptoms of diarrhoea and vomiting and good hygiene is important to prevent others from becoming infected.

Dr Foster added: “Many people enjoy open swimming and the considerable social and wellbeing benefits it brings. However, it is important to remember that anyone can become unwell from swimming in open water as there will always be micro-organisms present.”

British Triathlon, the governing body for triathlons in Great Britain, said the Environment Agency’s E. coli-positive tests of Roker beach were not published until after the weekend’s events and were outside the body of the water where its competitions took place. It said its own testing results passed the required standards for the event.