"That's what happens with a bug. It goes round, through kindys and schools," she said.
Tauranga Hospital's emergency department has dealt with 100 gastroenteritis cases since Christmas Eve, however it was not unusual for post-Christmas, clinical director Derek Sage said.
Gastroenteritis is an inflammation of the stomach and intestines from bacterial toxins or viral infection, often resulting in vomiting and diarrhoea.
At this time of year some of the cases were because of "dietary indiscretion" and lack of attention to food hygiene in the heat, Mr Sage said.
Camilla Wilkin, manager of Bay Med, said she hadn't noticed an influx of cases, but reiterated the seasonal trend.
"It's usually this time of year, with the warmer weather when we are all having barbecues and maybe not keeping the food as cold as we should do," she said.
"There is usually a small rise. In the summer time it's expected."
Jim Miller, medical officer of health for Toi Te Ora Public Health Service, said there was nothing unusual about the number and types of cases that had been brought to their attention.
But what they saw was usually "the tip of the iceberg".
"It's always difficult to say what goes on in the community. Quite possibly there has been a bug going around and it has not come to our attention."
Vomiting and diarrhoea symptoms that spread quickly among family members were likely caused by viral gastroenteritis, he said.
"It's quite infectious. Even with good hygiene it can be difficult to stop if people are getting it in the same household."
He advised staying at home until the symptoms had passed.
Public places, such as workplaces and schools, should be avoided for 48 hours as it could relapse in that time, he advised.
"Stay home and look after yourself. Make sure you drink lots."
The very young and old could become dehydrated and very unwell, in which case medical advice should be sought, Mr Miller said.
