The ban, approved at an extraordinary meeting of the Swiss Federal Council, comes into immediate effect and will apply at least until March 15, according to a statement by the Federal Council.
Federal Councilor Alain Berset said 15 cases of COVID-19 have been reported in the Alpine country as of Friday morning.
Affected by the ban, the 2020 Geneva Motor Show, scheduled to kick off next Thursday, was canceled.
In the case of public or private gatherings of fewer than 1,000 people, the Swiss federal government requires organizers, in conjunction with the competent authorities, to carry out a risk assessment to decide whether to hold the event.
Despite a predictable impact on public life, "the move is expected to provide effective protection to people... and to public health," stressed the federal government.