This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Regarding point sources epidemic, which is true? 
Select and explain. 
A. Rapid rise and fall, B. Only infections cause, C. Explosive, D. Secondary attack rate
A: Rapid rise and fall
Answer: A: Rapid rise and fall 
Explanation: The main features The epidemic curve rises and falls rapidly with no secondary waves The epidemics tend to be explosive there is a clustering of disease within a narrow interval of time All cases develop within one incubation period (refer park pano:64 23rd edition)