Three more people have been linked to an outbreak of cryptosporidiosis, according to health experts.

Tayside NHS Board said it was "virtually certain" that the outbreak originated at the Perth Leisure Pool last month.

The pool has been closed as a precaution while tests are carried out.

We are now virtually certain that the outbreak originated in Perth Leisure Pool

Dr Julie Cavanagh

Eight cases have already been confirmed among young children.

The health board said on Thursday that the number of suspected cases amongst friends and relatives of those children had now grown to seven.

Dr Julie Cavanagh, the head of the outbreak control team, said there was no cause for alarm as cryptosporidiosis was usually a "very mild illness".

It is caused by the cryptosporidium parasite, which sparked an alert in Glasgow and Clydebank following concerns about the levels in the water supply.

More than 150,000 people served by one reservoir were told to boil their water between Saturday night and Wednesday afternoon.

Accidental contamination

Cryptosporidium can cause severe diarrhoea, sickness, stomach cramps and a slight fever.

However, the outbreak in Perthshire was not linked to the public water supply, which NHS Tayside stressed was safe to drink.

Dr Cavanagh said: "We are now virtually certain that the outbreak originated in Perth Leisure Pool, most likely as the result of accidental faecal contamination.

Cryptosporidium can cause illness

"We can also begin to see a five-day window emerging during which we believe these children became infected - seven of them had visited the pool between 15 and 19 July."

The health board said none of the children, who are recovering at home, was seriously ill.

The pool is run by Perth and Kinross Leisure on behalf of Perth and Kinross Council.

Executive manager Peter Bing said: "We had no hesitation in following the advice of the outbreak control team to close the leisure pool to allow a full investigation to take place.

"We regret the inconvenience to the many people who use the pool every week, but public safety will always be our number one priority."