Estimation of the probable outbreak size of novel coronavirus (COVID-19) in social gathering events and industrial activities.

•R0 values vary depending on social activity and cluster type that induce infection spread.•We proposed a mathematical model to estimate the R0 of COVID-19 outbreaks in clusters.•A high R0=5 value is for wedding events, followed by religious gathering events (2.5).•The lowest R0 value was found in the industrial cluster (R0=2).•Our model is an important tool for epidemiology investigations by knowing when to stop.