Features of point source (single exposure) epidemicsThe exposure to the disease agent is brief and essentially simultaneous → single exposure. Because disease agent enters into all exposed persons at same time → the resultant cases all develop within one incubation period of the disease. The epidemic curve rises and falls rapidly. Because exposure is single (simultaneous) with no further exposure → No secondary wave (no secondary case). Epidemic tends to be explosive, there is clustering of cases within a narrow interval of time. Point source epidemics are mostly (not always) due to exposure to an infectious agent. Examples → Food poisoning, Bhopal gas tragedy, Minamata disease in Japan, Chernobyl tragedy.