A cluster of homeless patients presents with fever of unknown origin, hemoptysis, rapid weight loss, and night sweats. What is the most likely outbreak etiology?

• A. Influenza
• B. Tuberculosis (TB)
• C. Streptococcus pneumoniae infection
• D. Histoplasmosis

Answer: (B)

The pattern points to active pulmonary tuberculosis caused by Mycobacterium tuberculosis. The cluster of homeless patients with fever of unknown origin, hemoptysis, rapid weight loss, and night sweats fits TB’s typical presentation: a chronic illness that develops over weeks to months with systemic symptoms, plus a cough that can become productive with blood. Homeless populations in crowded, poorly ventilated settings are especially prone to airborne transmission, allowing the organism to spread and cause outbreaks.

Other options don’t fit as well. Influenza is usually acute with rapid onset of fever, cough, myalgias, and a shorter course, not the sustained weight loss and hemoptysis seen here. Streptococcus pneumoniae infection can cause pneumonia with fever and cough, but it typically presents more acutely and doesn’t commonly cause the prolonged systemic symptoms described. Histoplasmosis can imitate TB and cause similar symptoms, but outbreaks are tied to exposure to environments with bird or bat droppings and aren’t as strongly linked to homeless shelter settings.

Thus, the most likely outbreak etiology is tuberculosis, transmitted via airborne droplets in crowded shelters.