HIV transmission routes: Globally and in India, which is the most common mode of HIV transmission among adults?

Introduction / Context: Understanding predominant transmission routes guides prevention strategies and exam reasoning. Among adults worldwide, sexual transmission—particularly heterosexual contact in many regions—is the leading driver of new HIV infections.

Given Data / Assumptions:

• Adult transmission patterns (not pediatric).
• Population-level predominance rather than rare circumstances.
• Recognition that perinatal transmission pertains to infants, not adult spread.

Concept / Approach: HIV spreads via exposure to infectious body fluids across mucosal surfaces or via direct blood inoculation. Among adults, sexual contact is most common; parenteral spread (injecting drug use, transfusion) and occupational exposures are less frequent on a global scale. Casual oral routes and vectors are not credible pathways.

Step-by-Step Solution: Compare modes by population impact. Select sexual transmission as most prevalent in adult epidemics. Exclude perinatal as not adult-to-adult; exclude casual oral/vector myths.

Verification / Alternative check: Epidemiological surveillance consistently attributes the majority of adult cases to sexual exposure, with regional variation in the balance of heterosexual and MSM contributions.

Why Other Options Are Wrong: Parenteral is significant in specific subpopulations but not the global majority; perinatal concerns infants; casual oral and vector-borne routes are unsupported.

Common Pitfalls: Overgeneralizing from local outbreaks (e.g., high-IDU regions) to global patterns.

Final Answer: Sexual (heterosexual and/or MSM exposure).