For regions shut down due to Covid-19 to safely begin to reopen, we need ways to keep R — the average number of additional people infected by each infected person — under one, the threshold below which epidemics contract and ultimately die out. Among the proposals for how we can do this in the United States, one calls for frequent population-wide testing to identify and isolate those who are infected. Others suggest that the country will be hard-pressed to get through this without either prolonging lockdowns or intermittently reinstating them whenever infections rise until we have enough testing and contact tracing to control the spread or enough people become immune through infection or vaccination.
Image: Illustration by Jason Schneider
