HEALTH officials have launched an investigation on the River Ouse after 20 members of the same rowing club were struck down by a mystery illness.

In the past two weeks, the 20 members of the University of York Boat Club have all been struck down, all after training on the river.

The first to be hit by the vomiting and diarrhoea bug were the members of the senior men's team a fortnight ago, but since then all teams have been affected including the senior female squad and the men's and women's novice teams.

York Boat Club president Jillian Tongue , 21, was one of those affected. She said: "At first we thought it was an isolated case, but then we all came down with it. What was strange was that none of our friends or housemates was getting it and stomach bugs are normally very contagious.

"The only link between those suffering was that we had all been on the Ouse training, though with different teams and at different times. That's when we contacted the council and British Waterways because we knew something was up.

"It hasn't been the most pleasant time and while most of us are over it now there are some still feeling very weak.

"It has to be said that when we were rowing, our route took us past three sewage outlets and with the recent sunshine the smell was, shall we say, funky'. We have our suspicions and have now changed the route so it at least only goes past one."

The bug lasted up to three to five days and has left many of the squad still feeling tired and drained.

According to the City of York Council's health policy, the Ouse is not suitable for watersports. However, people may enter at their own peril.

Now the council has contacted the Health Protection Agency and has since requested tests from club members to make a diagnosis.

Weil's disease, which affects 10 per cent of all freshwater sites, is being considered as one of the potential causes.

Jillian said: "Being a rowing club we can't very well avoid the Ouse so we are now telling members to bring their own water bottles to training and put them in plastic bags while in the boats. They are also advised to protect any blisters or cuts, to avoid direct contact with the river water."

A City of York Council spokeswoman, said: "We were contacted by the rowing club over concerns about illness possibly associated with the river water. We have referred the matter on to the Health Protection Agency for their information."