Officials are considering ways to chlorinate Christchurch's water in an attempt to make the city's water supply safe.
Canterbury District Health Board's medical officer of health, Alistair Humphrey, says the city has avoided an outbreak of gastroentritis, though there have been sporadic cases of gastric infections.
Dr Humphrey says they believe these individuals have cleaned their teeth without boiling water first.
He says officials are now in a race against time to fix the water supply, and hopes it will be chlorinated soon.
He has praise for those Christchurch residents who have heeded advice to wash their hands, boil water and stay away from surface water and sewage spills.
Dr Humphrey says 10 cases of gastroenteritis were reported on Sunday, bringing the total to 22.