Containing the spread of COVID-19 (and the SARS-CoV-2 virus) involves an interlocking set of activities and none of these alone are a silver bullet to technically containing the virus. Due to the high natural rate of infection for COVID-19 (it has a basic reproductive rate or R0 of 2.3), a very radical set of steps are required to control its spread. The prime challenge is that we are always one step behind controlling the spread of the virus if we only self-isolate when we know we are infected. This is due to the virus spreading asymptomatically (while not presenting typical COVID or cold and/or flu symptoms). Modelling data shows that we can only stop the spread of the virus if those with symptoms are identified and isolated within two days. One cannot stop the spread of the disease if one is already likely to have passed on the illness. There are only two paths to reduce the number of people encountering a contagious person; a shelter-at-home style policy or targeted quarantines. Shelter-at-home is a course tool that severely impacts the economy whereas targeted quarantines are a more fine-grain approach that allows some people back to work. Contact tracing is a key component of targeted quarantines as potentially infected individuals need to be detected and then informed that they need to start self-isolation (and ideally this should be monitored).
