Swimming 'likely source' of triathlon norovirus

Health officials said that open-water swimming during the race was the "most likely source of infection"

Dozens of competitors who fell ill with norovirus at a triathlon were "likely" to have been infected during an open-water swimming event, health officials have said.

The UK leg of the World Triathlon Championship Series was held in Roker, Sunderland, in July last year.

An investigation by the UK Health Security Agency (UKHSA) was launched after almost 90 people reported symptoms of diarrhoea and vomiting, later put down to norovirus.

British Triathlon, which ran the event, said it welcomed the findings and was sorry that people became unwell.

Alongside elite competitors, over 1,200 people took part in the event on 29 and 30 July, which involved swimming, cycling and running.

However, 88 participants reported feeling unwell following the race.

Preliminary findings released in August said norovirus was the "most likely" explanation, and an investigation has now been completed by the UKHSA.

Officials said that open-water swimming during the race was the “most likely source of infection”.

This conclusion was reached in part as the only common exposure shared between those who fell ill was the fact that they all swam in the sea during the triathlon, officials added.

Microbiological testing

The UKHSA was able to take faecal samples from 47 competitors, the analysis of which revealed that 32 had a confirmed infection.

Norovirus was found in 23 samples, while other positive samples were caused by various other infections.

No infection was found in 15 of the 47 samples collected, but the UKHSA noted that as the specimens were collected a week after the race, any infection that caused symptoms may no longer have been present.

Water samples from the race area at Roker Beach, Sunderland, were collected by British Triathlon before and during the event, which officials said returned excellent water quality results.

But the UKHSA's report noted the microbiological testing of water can be "challenging", and these results did not exclude the possibility that contact with contaminated water was the possible cause of illness.

Northumbrian Water, which is responsible for water supply and public sewers in the North East, said its investigations had shown "there had been no discharges from any of our assets that might negatively impact water quality" at Roker.

It was not part of the report's remit to investigate wider issues about sewage management and bathing water quality, the UKHSA said.

'Successful event'

A spokesperson for British Triathlon thanked those affected for working with the UKSHA, enabling it to complete the report.

The spokesperson said that water tests conducted at the time were in line with World Triathlon Series guidelines for hosting such an event.

"The outbreak itself should not detract from what was a very successful event that attracted triathletes of all abilities to Sunderland," they added.