The Jarisch-Herxheimer reaction is a transient immunologic response to antimicrobial therapy most commonly seen with which type of infection?

• A. Influenza
• B. Pneumonia
• C. Syphilis
• D. Malaria

Answer: (C)

The main idea is that this reaction is an acute inflammatory response that occurs after starting antibiotics for infections caused by spirochetes. When spirochetes are rapidly killed, they release endotoxin-like lipoproteins that trigger a surge of inflammatory cytokines, producing fever, chills, rigors, and malaise within hours. Syphilis, caused by Treponema pallidum, is the classic example where this Jarisch-Herxheimer reaction is seen, making it the best answer here.

Influenza is viral, so antibiotics aren’t the trigger for this inflammatory burst. Pneumonia can be due to various pathogens, but the hallmark reaction isn’t tied to rapid lysis of spirochetes. Malaria is a protozoal infection; while fevers can flare after treatment, the Jarisch-Herxheimer reaction is not the classic pattern described for malaria.