https://www.mercurynews.com/2020/03/11/san-francisco-to-ban-public-gatherings-of-more-than-1000-people/

As coronavirus continued its spread and public officials warned residents to avoid large gatherings, the city of San Francisco moved to shut down major concerts, public sporting events and more.

The city’s mayor, London Breed, announced Wednesday morning that the city’s health officer has issued a public health order prohibiting any group gatherings of 1,000 people or more, a move that came after a similar order in Santa Clara County earlier this week. Officials in Alameda and Contra Costa counties are sternly warning residents to avoid gatherings, though neither county had issued bans by midday Wednesday.