PYEONGCHANG, South Korea (Reuters) - Pyeongchang Winter Olympics organizers said on Saturday that 11 new cases of a virus that causes vomiting and diarrhea had been confirmed at the Games, bringing the total to 139.

The number of new norovirus cases is a steep drop-off from the 42 new cases confirmed on Thursday and 54 a day earlier.

The virus had broken out in the leadup to Friday’s opening ceremony in Pyeongchang and led to some 1,200 security staff being quarantined. Organizers had to call in military personnel to replace them.

As yet, no athletes have been confirmed to have contracted the highly contagious virus. An outbreak at last year’s World Athletics Championship in London forced competitors from several countries to miss events.

POCOG said several agencies were cooperating to stifle the outbreak, with water quality being tested and inspections taking place at venues, restaurants, hotels and worker accommodation.