The cause of this week's vomiting and diarrhoea outbreak remains unsolved as test results are yet to come back.

Hawke's Bay District Health Board issued a press release on Wednesday urging parents to keep sick children home as a vomiting and diarrhoea bug was circulating through the community.

A spokeswoman for the board yesterday said they were still unsure what the cause was because the test results expected near the end of the week had not arrived, but there were suspicions it was a viral infection.

She could not confirm how many cases there had been, only that it was widespread and affected all ages.

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It had been reported that a number of children at Fraser Town School, in Wairoa, had been affected by the bug and it appeared to be recurring, with children who had recovered from the bug getting sick a second time.

But at the other end of Hawke's Bay, Waipukurau Primary School principal Tim Hocquard said there had been no cases at the school.

"Perhaps it's a bit colder here, it certainly hasn't hit us yet," he said.

There had been no cases confirmed at a Taradale retirement village.

Medical Officer of Health Rachel Eyre said symptoms appeared to ease after about 12 hours with most people experiencing vomiting, nausea, abdominal pain and general aches and pains.

"While there didn't appear to be any cause for the outbreak, which seemed to be widespread throughout Hawke's Bay, it was most likely being spread from person to person and likely to be a virus," she said.

Dr Eyre said anyone with vomiting or diarrhoea should stay away from work and sick children should be kept home for at least 48 hours after symptoms had cleared.

Careful attention to hand washing would help prevent the bug spreading.

People with stomach bugs can be infectious after the symptoms stop and on some occasions for up to two weeks, so it was important not to swim in public swimming pools for two weeks, she said.