Consider the following diseases (1). Diphtheria (2). Chickenpox (3). Smallpox Which of the above diseases has/have been eradicated in India?

The answer is B (only Smallpox). Eradication means permanent reduction of a disease to zero cases worldwide, so no further vaccination is needed. Smallpox is the only human disease eradicated so far. Its last indigenous case in India was in 1975, and WHO certified global eradication in 1980.

• Diphtheria (1): Not eradicated. It still occurs in pockets of India and is controlled through DPT vaccination under the Universal Immunisation Programme.
• Chickenpox (2): Not eradicated. Varicella is still endemic. Vaccines exist and are used in some programmes, but the disease has not been eliminated.
• Smallpox (3): Correct. It is eradicated, and the variola virus stocks are held only in two WHO-approved labs.

The core concept is the difference between eradication, elimination and control. Eradication is the strictest. Polio is the one to watch: India was declared polio-free by WHO in 2014, but the disease is not yet eradicated globally. For Mains GS-II, this links to vaccine policy, public health governance and the role of global bodies like WHO.

Trap: Aspirants often treat "controlled" or "near-eliminated" diseases as eradicated. Remember that only smallpox qualifies among human diseases.