Question

Which of the following is least infectious?

• A. Leprosy
• B. Hepatitis
• C. Tuberculosis
• D. Conjunctivitis

Hint:

Leprosy needs years of close contact to spread and is one of the least contagious diseases known, unlike the other three options.

Answer 1

The Correct Option is A

Step 1: Understand what infectivity means.
Infectivity is how easily a disease spreads from one person to another. A highly infectious disease spreads through brief or casual contact, while a disease with low infectivity needs long, close, or repeated contact before it passes on.

Step 2: Look at leprosy.
Leprosy is caused by the bacterium Mycobacterium leprae. Even though it was once greatly feared, it actually spreads very slowly and needs years of close and prolonged contact with an untreated patient, usually through nasal droplets. Most people who are exposed never catch it, because the natural immunity in humans against this bacterium is high and only a small fraction of the population is genuinely susceptible.

Step 3: Look at the other three diseases.
Hepatitis, especially the common types spread through contaminated food, water, blood, or body fluids, moves through a population quite easily wherever hygiene is poor or exposure to infected blood happens.
Tuberculosis spreads through airborne droplets released when an infected person coughs or sneezes, and a single untreated patient can pass it to many people sharing the same air over time.
Conjunctivitis, or pink eye, spreads very fast through direct contact with eye discharge, contaminated hands, towels, or surfaces, and is well known for causing quick outbreaks in schools and homes.

Step 4: Compare and conclude.
Out of the four, leprosy clearly needs the longest and closest contact to transmit and has the lowest natural spread rate. Hepatitis, tuberculosis, and conjunctivitis all spread far more readily by comparison.
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