From the CDC: https://www.cdc.gov/coronavirus/2019-ncov/community/large-events/mass-gatherings-ready-for-covid-19.html
Get Your Mass Gatherings or Large Community Events Ready
Interim Guidance for Coronavirus Disease 2019 (COVID-19)
Guidance as of 3/15/2020
Large events and mass gatherings can contribute to the spread of COVID-19 in the United States via travelers who attend these events and introduce the virus to new communities. Examples of large events and mass gatherings include conferences, festivals, parades, concerts, sporting events, weddings, and other types of assemblies. These events can be planned not only by organizations and communities but also by individuals.
Therefore, CDC, in accordance with its guidance for large events and mass gatherings, recommends that for the next 8 weeks, organizers (whether groups or individuals) cancel or postpone in-person events that consist of 50 people or more throughout the United States.
Events of any size should only be continued if they can be carried out with adherence to guidelines for protecting vulnerable populations, hand hygiene, and social distancing. When feasible, organizers could modify events to be virtual.
This recommendation does not apply to the day to day operation of organizations such as schools, institutes of higher learning, or businesses. This recommendation is made in an attempt to reduce introduction of the virus into new communities and to slow the spread of infection in communities already affected by the virus. This recommendation is not intended to supersede the advice of local public health officials.
This interim guidance is intended for organizers and staff responsible for planning mass gatherings or large community events in the United States. A mass gathering is a planned or spontaneous event with a large number of people in attendance that could strain the planning and response resources of the community hosting the event, such as a concert, festival, conference, or sporting event. Guidance specific to schools and childcare settings, institutions of higher education, and community- and faith-based organizations can be found on CDC’s website focused on prevention COVID-19 spread in communities.
COVID-19 is an emerging respiratory disease and there is more to learn about its transmission, clinical course, and populations at increased risk of disease and complications (see How COVID-19 Spreads). Everyone can do their part to help plan, prepare, and respond to this emerging public health threat.
As the COVID-19 outbreak evolves, CDC strongly encourages event organizers and staff to prepare for the possibility of outbreaks in their communities. Creating an emergency plan for mass gatherings and large community events can help protect you and the health of your event participants and the local community.
CDC has developed recommended actions for preventing the spread of COVID-19 at mass gatherings and large community events. This guidance suggests strategies to help you plan for and implement ways in which to better protect all involved in a mass gathering.
Organizers should continually assess, based on current conditions, whether to postpone, cancel, or significantly reduce the number of attendees (if possible) for mass gatherings. Listed below are some considerations organizers should keep in mind as they make decisions about whether to postpone or cancel an event. If organizers decide to proceed with an event they should consult the “Steps to Plan, Prepare, and Proceed with a Mass Gathering” section of this document.
