Common source outbreaks where the source has infected cases at one particular geographical location, during a short period of time, are called 'point source outbreaks'. In such situations the source is said to be located 'at a single point in time and place'. These outbreaks have a typical bell shaped epidemic curve, that increases sharply, peaks and then decline sharply, which reflects the normal distribution of the incubation period of the causative agent in humans. For this reason, the epidemic curve of a point source outbreak can help us identify the moment of transmission (i.e. when all cases have been exposed to the source).