Norovirus is highly contagious and can also be spread through food or water contamination.
"The 1,200-odd people were pulled out from their duties," an official of the Pyeongchang Olympic Organizing Committee told AFP. "They were replaced by some 900 military soldiers."
Health authorities were investigating the origin of the virus, he said.
The security guards, all employees from a security company, had been accommodated at a youth training centre in Pyeongchang, separate from the athletes' village.