This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Regarding point source epidemic, false statement (s) is/are:a) Rapid rise & fallb) Only infectious disease can causec) Explosived) Cases occur even after incubation periode) No secondary wave 
Select and explain. 
A. ce, B. bd, C. cde, D. eb
B: bd
Answer: B: bd 
Explanation: Features of point source (single exposure) epidemics 

The 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.