Chief Health Officer Dr Paul Kelly said a handful of staff and children had been infected since he was first notified last Thursday.

It was the first outbreak of 2016 to involve ACT Health.

"But the year is young, and we do have an upsurge at this time of year, particularly in childcares," Dr Kelly said.

Despite being highly infectious, norovirus doesn't tend to amplify from childcares into the community. But even one case could become problematic if the child became dehydrated, Dr Kelly said.

"That can happen quite quickly, and then when you start to get the hot weather the symptoms of dehydration can become quite dangerous," he said.

"So if a child starts to become listless, sleepy and not interacting in the normal way, these can be danger signs, particularly if it's associated with not having wet nappies or not going to the toilet."

Typical symptoms include vomiting, diarrhoea and abdominal pain lasting between one to two days.

Keeping fluid up is the only treatment. Severe dehydration requires medical attention.

Dr Kelly said infected children should be kept at home for 48 hours after the last symptom.

Both kids and carers must diligently wash hands and clean affected areas.

"It spreads not only by direct contact with bodily fluid but also by hands touching and where the vomit ends up," Dr Kelly said.

"Once a child goes home, it can spread through the family."

Children are not the only people who are vulnerable to catching the illness when sharing space or food.

A Canberra woman was one of 150 people who fell ill on a musical cruise in October featuring Australian and international stars and Opera Australia performers.

Six months earlier, a Canberra nursing home was in lockdown after the diagnosis of gastroenteritis in a number of residents, leading to restricted access for family to visit residents.

Fifty-three students caught the virus after an ANU end of year celebration at Burgmann College in 2014.