This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other Key Definitions & Concepts, Subject name: Social & Preventive Medicine
[{'content': 'Index case refer to:- \nSelect and explain. \nA. First case of disease in community, B. All cases that occurs after primary case, C. First case which comes into notice of investigator and usually it is secondary case, D. None of above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: First case of a communicable disease introduced into the population unit, being studied Primary case First case to come to attention of investigator Index case Developing from contact with primary case Secondary case An individual who has signs and symptoms connected to the suspected pathogens Suspect case', 'role': 'assistant'}]