Bacillus anthracis can infect humans through which routes?

• A. Mucosal contact only
• B. Ocular and cutaneous only
• C. Respiratory, gastrointestinal, and cutaneous
• D. Oral ingestion only

Answer: (C)

Bacillus anthracis can infect humans through three primary routes: cutaneous, inhalational (respiratory), and gastrointestinal. Spores entering through breaks in the skin cause cutaneous anthrax, typically presenting with a characteristic eschar. Inhalational exposure occurs when spores are inhaled, leading to a severe, often rapidly progressive respiratory illness. Ingestion of contaminated meat can lead to gastrointestinal anthrax, which can cause intense abdominal symptoms and systemic infection. These three routes are the best-supported, widely recognized pathways for human infection.

Ocular infection can occur but is rare and not considered a principal route of acquisition, and alternatives that restrict infection to only mucosal contact or only oral ingestion do not capture the full range of common transmission pathways.