R-Value
In any epidemic, R(t) is the measure known as the effective reproduction number. It's the number of people who become infected per infectious person at time.
The R-Value helps us understand how effective our mesure have been controlling an outbrea. It gives us vital information about whether we should increase or reduce restrictions based on our competing goals of economic prosperity and human safety.
Well-respected epidemiologists argue tracking R(t) is the only way to manage through a crisis.