A 34-year-old man develops a flu-like illness that is accompanied by a red, flat, round rash on his leg that progressively expanded outward over the course of a week. As the rash expanded, the center of the rash slowly turned clear. What was the most likely event that introduced the pathogen for this patient’s presentation?
Airborne droplet inhalation
Unprotected sexual contact
correct answer: D
The rash described is erythema chronicum migrans (ECM), the primary lesion of Lyme disease, which is caused by Borrelia burgdorferi. A tick bite (choice D) from the Ixodes tick transmits the spirochete from the white-footed mouse reservoir, and the illness starts about 10 days after the bite with a single ECM rash, a flu-like illness, and regional lymphadenopathy.
Lyme disease is not transmitted via airborne droplets, fecal-oral, needle-sticks, or unprotected sexual contact.