What is the approximate risk of acquiring HIV from a needle-stick exposure?

What is the approximate risk of acquiring HIV from a needle-stick exposure?

• A. 0.03%
• B. 30%
• C. 0.3%
• D. 3%

Answer: (C)

The main idea is that transmission from a needle-stick is relatively unlikely but possible. For an exposure to an HIV-positive source, the typical approximate risk is 0.3% per needle-stick, meaning about 3 infections in 1,000 exposures. This figure reflects the fact that the skin and tissues provide a barrier, the amount of virus entering the body is variable, and not all exposures lead to infection. The other numbers are not consistent with standard estimates: 0.03% is much too low, 3% and 30% would imply far higher transmission than is observed. In practice, measures like rapid initiation of post-exposure prophylaxis can further reduce this risk.

The main idea is that transmission from a needle-stick is relatively unlikely but possible. For an exposure to an HIV-positive source, the typical approximate risk is 0.3% per needle-stick, meaning about 3 infections in 1,000 exposures. This figure reflects the fact that the skin and tissues provide a barrier, the amount of virus entering the body is variable, and not all exposures lead to infection. The other numbers are not consistent with standard estimates: 0.03% is much too low, 3% and 30% would imply far higher transmission than is observed. In practice, measures like rapid initiation of post-exposure prophylaxis can further reduce this risk.