Carriers are important source of infection in all, EXCEPT:
The question is about diseases where carriers aren't a significant source of infection. Common examples where carriers are important include diseases like typhoid fever (H. pylori?), no, wait, typhoid is caused by Salmonella Typhi. Carriers like Mary Mallon were famous. Hepatitis B and C also have carriers. HIV is another example. But some diseases don't have carriers because they don't have an asymptomatic phase. For example, measles is highly contagious but carriers aren't a major source. Or maybe pertussis? Wait, whooping cough can have asymptomatic or mild cases, so carriers might spread. Another example: tetanus doesn't spread from person to person, so carriers aren't an issue. But the question is about the exception. So the answer is likely a disease where carriers aren't a significant source. Let me think of the options. If the options were, say, A. Hepatitis B, B. HIV, C. Measles, D. Gonorrhea. Then the answer would be C. Measles because carriers aren't a major source. Measles is spread through acute infection, not carriers. Carriers are important in Hep B, HIV, and Gonorrhea. So the correct answer would be the one where carriers aren't a source. Another example: Rabies? No, that's not a carrier disease. So the correct answer is likely a disease that's not spread via carriers. The user's correct answer is missing, but based on typical questions like this, the answer is often measles or perhaps chickenpox. But I need to make sure. Let me check standard medical textbooks. In microbiology, diseases with carriers include typhoid fever, hepatitis B, HIV, and meningococcus. Diseases without carriers include measles, mumps, rubella. So the answer is likely one of these. The question is probably looking for an infectious disease that does not have a carrier state as a significant source of transmission. Therefore, the correct answer would be the disease where carriers are not a major concern. For example, measles. So the options might have included measles as the correct answer. Therefore, the correct answer is C. Measles. Now, structuring the explanation accordingly.
**Core Concept**
This question tests understanding of **carrier states in infectious diseases**. A carrier is an individual who harbors a pathogen without showing symptoms but can transmit it to others. Not all infections maintain a significant carrier state; diseases with prolonged asymptomatic carriage (e.g., Hepatitis B, HIV) are notable exceptions.
**Why the Correct Answer is Right**
**Measles** (if it were the correct answer) lacks a significant carrier state because it is an **acute, highly contagious viral infection** with no asymptomatic or chronic phase. Transmission occurs only during the brief infectious period when symptoms are evident. Unlike Hepatitis B or HIV, there is no prolonged viral reservoir in asymptomatic individuals. The immune response