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
The following set of words can be used synonymously in epidemiology 
Select and explain. 
A. Source and reservoir, B. Index and primary case, C. Latent infection and subclinical infection, D. Serial interval and incubation period
C: Latent infection and subclinical infection
Answer: C: Latent infection and subclinical infection 
Explanation: in latent infection the host does not shed the infectious agent which lies dormant within the host without symptoms.the subclinical cases are referred to as inapparent,cove,missed or aboive cases.they are equally impoant as sources of imfections.the term primary case is the first case of a communicable disease and index case refers to the first case that comes to the attention of an investigator.ref;parks textbook ,22 nd ed,pg no 92