It is an organizing committee’s nightmare: A virus stalking the venues of an imminent, top-tier global sporting event. But this is exactly the situation facing organizers of the 2018 Pyeongchang Winter Olympics, which kick off in South Korea in just two days.

Some 1,200 security workers – persons tasked with checking visitors as they enter venues and facilities – have been confined to their rooms, Yonhap News reported, pending testing. This follows an outbreak of norovirus in Pyeongchang, which has laid up 41 security workers since Monday. The workers will be replaced by activity duty troops, according to news reports.

It is not clear where the affected persons, whose accommodation is close to the main skis slopes, contracted the virus. Early reports suggested the virus was identified in the water in the workers’ showers and sinks; more recent reports indicate that it was food-related.

While the virus is not deadly, and most patients recover within two days, it is highly infectious. It causes stomach ache, nausea, vomiting and diarrhea – conditions that could severely impair the performance of athletes.

The International Olympic Committee is distributing leaflets warning of the virus, and the areas of the outbreak have been disinfected. Preventative measures include washing hands regularly.