In February, 156 people affected by the cryptosporidium parasite were admitted to hospitals across Victoria, compared with the February average of 60. Since January, Brimbank has reported 17 cases, Melton 15, Wyndham 11, Hume eight, Maribyrnong four and Hobsons Bay two.

Victoria's chief health officer John Carnie said there was a direct link between an increase in gastroenteritis and more people using local pools due to the hot weather.

Cryptosporidium is usually caused by swallowing water contaminated by fecal matter, person-to-person contact and contact with animals.

Swimming pools can harbour the parasite as it is not killed by normal levels of chlorination.

Dr Carnie said symptoms included watery diarrhoea, stomach cramps and vomiting.

A spokesman for the Department of Human Services said swimming pool operators had procedures to deal with contaminated water.

Maribyrnong Aquatic Centre manager Lyn Celotti said swimmers were advised to not use the pool if they had gastroenteritis. She urged parents of young children to be careful about hygiene after changing nappies, to reduce the risk of contamination.