The spread of Covid-19 appears to be heavily dependent on individuals who are "super-spreaders" and on "super-spreading events". For example, the guy who was in

The spread of Covid-19 appears to be heavily dependent on individuals who are "super-spreaders" and on "super-spreading events". For example, the guy who was involved in horse-racing at Yonkers, the choir practice in Washington, the conference at Boston. So a simple model where each case results in R new infections doesn't capture this at all. Instead, networks of infection appear to be like other social networks where some nodes are much more highly connected than other nodes. The task that colleges face is to ensure that students with large social networks don't infect their contacts and to ensure that large events conducive to infection don't happen. Otherwise, no amount of wiping doorknobs and fogging classrooms with disinfectant will be effective.