Key Points:

A stomach bug that forced the suspension of a junior badminton tournament in Christchurch has been sourced to a caterer working at the opening dinner.

Vomiting and diarrhoea affected more than 90 people at the Australasian under-17 Junior Badminton Championships at Cowles Stadium.

Players, coaches and officials were all affected, while the caterer became ill the night after the dinner, within a few hours of preparing a rice salad.

Public health officials called to identify the source of the outbreak said on Tuesday the gut-wrenching, highly infectious norovirus was the most likely cause.

Canterbury medical officer of health Alistair Humphrey confirmed today that the norovirus had been traced to a caterer.

The Canterbury District Health Board's community and public health division identified the source as one of the contract workers working in the kitchen during the shared dinner held as part of the tournament's opening ceremonies.

"Though the worker could not have known it at the time, they were likely to have been shedding virus during the preparation of the food," Dr Humphrey said.

He said the pattern of illness -- a short incubation period, with short-lived symptoms of vomiting and diarrhoea -- was consistent with a norovirus outbreak.

Norovirus was spread directly from person to person, but could involve an "intermediate vector, such as food".

Computer analysis of data from questionnaires completed by tournament competitors and officials pointed to the rice salad as the most striking risk factor.

Dr Humphrey said the tournament organising committee's decision to suspend play for 24 hours on Wednesday helped bring the outbreak to an end, with no further cases reported since then.

The public health investigation team inspected the kitchen facilities and was satisfied catering was provided to a high standard. No action would be taken against the firm.

"It was unfortunate that one worker, who did not have symptoms until shortly after the dinner, was shedding norovirus during food preparation," he said.

No punitive action was required.

Tournament director Lyndsay Dick, who also became ill during the outbreak, said play was back to normal today.

"There's absolutely no effects today," she said. "Some of the kids are not back to full eating yet, but you wouldn't know (people had been sick) if you walked in here now."

Ms Dick said a few teams events had been cancelled but she doubted it would affect overall results.

The tournament is scheduled to end tomorrow night.

"It's good that we can finish. Our scheduling is a bit tight, but we'll get through it okay," she said

- NZPA