South Korea has deployed 900 military personnel after some 1,200 security guards were pulled from duty because of a norovirus outbreak at Winter Olympic facilities in PyeongChang.

The Korea Herald said 41 security guards suffered a sudden onset of vomiting and diarrhea Sunday and have been hospitalized.

Today, CNN is reporting that more than 1,000 security guards were replaced with military personnel, just days before the opening of the 2018 Winter Olympics.

The guards were withdrawn Monday afternoon to prevent the spread of the highly contagious virus, a statement from the PyeongChang Olympics committee said.

“The military personnel … will be responsible for security checks of the 20 venues as they take up jobs such as security searches, previously done by civilian safety personnel, until the patients’ condition is normalized,” the statement said.

The security guards were reported to have been staying at the Ho-lab Mountain Ode Youth Training Center in PyeongChang, Gangwon Province.

The government plans to investigate whether other security employees are infected and will suspend food distribution and inspect the groundwater, CNN reported.

The first suspected case of norovirus was identified this past Thursday. The Olympics organizing committee and Korea’s Centers for Disease Control and Prevention are under fire for their delayed response in handling the situation.

Norovirus is the most common cause of acute gastroenteritis, or infection of the stomach and intestines, due to food poisoning. Highly contagious and active at low temperatures, the virus causes stomach pain, nausea, diarrhea and vomiting. People can become infected by eating or drinking contaminated substances, touching contaminated surfaces and coming into contact with an infected individual.

With a 24- to 48-hour incubation period, the virus can also cause muscle aches, headaches and fever. In severe cases, one may feel dehydrated and experience severe abdominal pain.

There is no available vaccine or treatment options for the virus. Patients usually recover within one to three days.

Prevention is key when dealing with the norovirus, and experts advise good handwashing and disinfecting contaminated objects and surfaces. Heating contaminated objects to 70 degrees F for five minutes or 212 degrees F for a minute can kill the virus.

The Olympic organizing committee plans to monitor all 18 accommodations that made use of the suspect groundwater and food preparations, as well as distribute disinfectants to accommodations in Gangwon Province, the Korea Herald reported.

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