The security staff members were tested for the virus and kept in their rooms while they awaited results after 41 members of staff suffered diarrhea and vomiting. Games chief Lee Hee-beom said the South Korean disease control center and other government agencies were discussing counter-measures. Officials are looking into the cause of the outbreak by examining the food and water facilities the affected personnel have been using. The security staff members have been replaced with military personnel until their test results are available, and Lee assured a news conference that the potential outbreak would have no effect on security at the Games.

Norovirus is a highly contagious illness that causes stomach cramps and vomiting. Last year at the world athletics championship in London, an outbreak that spread through a hotel prevented some athletes from competing.

Unusually cold weather may be partially to blame for the illness in South Korea. The 2018 Winter Olympics may be the coldest since the 1994 Games in Norway. Lee said the cold weather has led some people to give up their tickets to the opening ceremony, which will take place at the open-air Olympic stadium on Friday. In December, the Associated Press reported that six people who attended a concert at the stadium got hypothermia.

The organizing committee is taking steps to ensure that the Games are not delayed by weather. For instance, Lee said they were installing wind screens at the ski jumping venue to avoid delays caused by high gusts.