Epidemiological data suggests that 80% of COVID-19 cases can be traced to just 20% of those infected with SARS-CoV-2.
The latest Doherty Institute modelling also indicates the spectre of 'unidentified community transmission' is very unlikely indeed.
I'm here to say: make sure you read beyond the headlines.
Epidemiologists want to quickly identify any emerging disease's potential to spread far and wide. Dependent on a number of factors, this R0 number helps them figure that out and plan accordingly.