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
The infectivity of a patient with diphtheria is ? 
Select and explain. 
A. Till cough subsides, B. Till patient is febrile, C. Life long, D. For 15 days after infection
D: For 15 days after infection
Answer: D: For 15 days after infection 
Explanation: Ans. is 'd' i.e., For 15 days after infection o The period of infectivity may vary from 14 to 28 days from the onset of the disease, but carriers may remain infective for much longer period. o A case or carrier may be considered non-communicable when at least 2 cultures properly obtained from nose and throat, 24 hours apa, are negative for diphtheria bacilli.