What is the first identified case of an infectious disease in an individual/community called?

Correct option is B

Sol. The primary case is the first individual in a community to contract and introduce an infectious disease to a population. This person may or may not be the first detected case but is the source of infection for others. The index case, on the other hand, is simply the first diagnosed or reported case, which might not necessarily be the first person infected.
Explanation of each option:
· (a) Index case – Incorrect. The index case is the first identified case that comes to the attention of health authorities but may not be the true first infected person in the outbreak.
· (b) Primary case – Correct answer. The first person to introduce the disease to a population, whether or not they are diagnosed first. They initiate the chain of transmission.
· (c) Secondary case – Refers to individuals who contract the disease from the primary case, indicating subsequent transmission. They do not start the outbreak but contribute to its spread.
· (d) Carrier – A person who harbors the pathogen without showing symptoms but can transmit the infection to others unknowingly. Carriers may contribute to disease spread but are not necessarily the first case.