This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, 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: Unless treated, 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 periods. Ref:PARK&;S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICINE , 23rd edition , Page 160