**Question:** Incubatory carrier seen in - a) Cholera b) Bubonic plague c) Mumps d) Measles e) Influenza

**Core Concept:** An incubatory carrier refers to a stage in the course of an infection where the individual is infected with a pathogen but does not display any symptoms or signs of the disease. This stage is often followed by the onset of clinical symptoms.

**Why the Correct Answer is Right:** The correct answer, **Option D: Measles**, is related to the incubatory carrier stage because measles is a highly contagious viral disease caused by the measles virus (Morbillivirus). The incubation period for measles ranges from 10 to 12 days, during which an infected individual may serve as an incubatory carrier without showing any symptoms. This allows the virus to spread to other individuals before the infected person develops the characteristic rash and symptoms of the disease.

**Why Each Wrong Option is Incorrect:**

**Option A: Cholera** is an infection caused by the bacterium Vibrio cholerae, primarily affecting the small intestine and leading to severe diarrhea. Cholera does not involve an incubatory carrier stage due to the rapid onset of symptoms.

**Option B: Bubonic plague** is caused by the bacterium Yersinia pestis and primarily affects the lymph nodes (buboes). Unlike measles, plague has a short incubation period and typically presents with severe symptoms soon after infection.

**Option C: Mumps** is an infection caused by the virus Paramyxovirus and primarily affects the salivary glands. Mumps also lacks an incubatory carrier stage, as symptoms typically develop within a few days after infection.

**Option E: Influenza** is an infection caused by the influenza virus and affects the respiratory system. The incubation period for influenza ranges from 1 to 4 days, during which an infected individual may serve as an incubatory carrier. However, in comparison to measles, the duration of the incubatory carrier stage in influenza is shorter, making measles a better example of an incubatory carrier stage.

**Clinical Pearls:** Understanding the concept of an incubatory carrier stage is crucial for public health interventions, contact tracing, and patient management. It helps healthcare professionals to identify and isolate individuals in the incubatory stage, preventing further transmission of the disease to other individuals.