False regarding a propagated epidemic is -

Propagated epidemics Propagated epidemic is most often of infectious origin. - It results from person to person transmission. Source of disease agent is not common to all cases. Every new case becomes the source for others. The epidemic usually shows a gradual rise and tails off over a much longer period of time. The speed of spread depends upon herd immunity, opportunities for contact and secondary attack rate. Propagated epidemics are more likely to occur where large number of susceptible are aggregated, or where there is a regular supply of new susceptible individuals (e.g. birth, immigrants) lowering herd immunity. Transmission continues until the number of susceptible is depleted or susceptible individuals are no longer exposed to infected persons or intermediary vectors. Epidemic continues over more than one incubation period. Secondary waves are seen. Examples - epidemic of polio and Hepatitis A. Also know A typical type of epidemic is epidemic of cholera. It starts as common source-epidemic → most of the initial cases acquire the disease from a common source (e.g. a well with contaminated water). Then it continues as a propagated epidemic → these cases become the source for the other persons in their close vicinity. So it has a sharp peak but tails of gradually over a longer period of time.