How to deal with the COVID-19 outbreak while organizing a conference? I am an organizer for a graduate student conference in Mathematics occurring in April. My co-organizers and I are debating on a plan for what to do if the COVID-19 outbreak in the United States worsens. Right now, most of the participants are from states with no confirmed cases of the coronavirus, but this may change rapidly as the situation develops between now and the conference.

This is an issue other conferences throughout history have surely had to deal with, so I wanted to ask StackExchange if there were any best practices around for dealing with an issue like this. Some questions:


How far out should the go/no go decision be made? If the conference is late April, should we be planning to let participants and speakers know by early April so they can cancel flights and so on?
What criteria should best inform whether we cancel or not? Number of cases in the participants' states for instance?
In the event we are to cancel the conference, how can we still give the speakers a chance to advertise their results? Have there been successful "video conferences" before where the organizers collect video for each talk and then upload them and participants can make comments?
Regarding remote conferences, these have been successful. Often the motivating factor has been mitigating climate impact. For example, Yale Climate Connections wrote an article giving advice for running virtual conferences. Author Sara Peach presents three kinds of virtual conferencing, all of which have been done successfully: 


remote presentations in a traditional conference format. If people choose to not travel, they can still remote in or follow the session on social media. (Example: AGU)
hub-based conference, where people gather in regional clusters. Each hub has some of its own content but are able to watch each other's presentations. (Example: International Conference on Music Perception and Cognition)
an entirely remote conference, where people record and upload videos of presentations and conferencegoers have weeks to ask questions and interact. (Example: A Nearly Carbon-Neutral Conference Model)


I'll add that an entirely virtual synchronous conference has also been done successfully. One example is NACADA, the Global Community for Academic Advising, which ran a 24-hour live-streaming virtual conference. 

The mixed-conference or hub models may or may not be feasible, since they would still involve people gathering in some models, and you aren't sure yet whether that will be feasible on any scale. Also, developing regional hubs would take time you don't have.  Thus, if you decide to go entirely virtual, a synchronous-with-live-streaming conference and a asynchronous recorded approach have been done, and the resources linked should provide a way to start researching or planning that model. I also advise contacting your own IT department about the possibility.