The number of confirmed cases of the highly contagious norovirus at the Pyeongchang Winter Olympics jumped by 42 to 128, organizers said on Thursday, on the eve of the Games.

No athletes are among those taken ill with the stomach bug, which causes diarrhea and vomiting, and organizers say they are doing everything they can to keep it that way.

Any illness spreading to the competitors -- particularly one of the star names -- would be a major embarrassment to hosts South Korea.

Hundreds of soldiers have been drafted in to guard Olympic venues after 1,200 security staff were withdrawn and quarantined earlier this week over the outbreak, which can also be spread through food or water contamination.

Of the 42 new cases, most were among security staff and they have been quarantined and are being monitored.

Local organizers POCOG have rushed out hand sanitizers to venues and launched an information campaign encouraging people to wash their hands thoroughly and regularly.