Eighty-six cases of norovirus have been confirmed among personnel working at the Winter Olympics in Pyeongchang, the Korean Centre for Disease Control and Prevention said on Wednesday.
Centre director Kim Hyun-jun said there were 58 cases at the Odaesan Youth Centre, which is housing 1,200 security personnel who have been quarantined. Nine hundred military personnel were called in to address a shortfall in security as a result.
Twelve police officers have contracted norovirus, while three food preparation staff working at the media accommodation village have also become ill. No athletes have been affected.
"Among the athletes we don't have any who have contracted norovirus," Kim said.
"Norovirus is highly contagious so we don't know the geographical frequency of the outbreak. We don't know when the outbreak will occur again and under which circumstances.
"The peak season for norovirus is January and February so unfortunately we're in a bad time of year where outbreaks occur.
"In order to stop the further outbreak of the virus we're quarantining patients beginning from the diagnosis to the treatment. We're going to minimise this outbreak."
The unpleasant but rarely serious illness is often caught through close contact or by touching contaminated surfaces or objects.
Norovirus can result in vomiting and diarrhoea, and those affected are encouraged to drink fluids to avoid dehydration.