Zidovudine is most directly used to treat infection with which pathogen?

• A. Candidiasis
• B. Herpes simplex virus
• C. Human immunodeficiency virus
• D. Respiratory syncytial virus

Answer: (C)

Zidovudine is an antiretroviral that acts as a nucleoside reverse transcriptase inhibitor. It is a thymidine analog that, once phosphorylated inside cells, inhibits HIV reverse transcriptase, preventing the viral DNA from being synthesized and thereby stopping HIV replication. Because its mechanism targets the reverse transcription step unique to retroviruses, it is used to treat HIV infection (and to reduce mother-to-child transmission), not fungal infections like candidiasis, herpesviruses like HSV, or RSV. The pathogens listed include a fungus, a DNA virus treated with other antivirals, and an RNA virus managed differently, so zidovudine most directly addresses HIV.