Which population group is at higher risk for severe Legionella disease?

• A. Immunocompromised individuals, the elderly, and smokers
• B. Healthy young adults
• C. Children under 5
• D. Athletes

Answer: (A)

The risk of severe Legionella disease rises when the body's defenses in the lungs are weaker or less able to clear the bacteria. Immunocompromised individuals have a reduced ability to control intracellular pathogens like Legionella. The elderly often have less physiologic reserve and more comorbidities, which worsens outcomes. Smokers have damaged airways and impaired mucociliary clearance, making it easier for the bacteria to invade and cause extensive pneumonia. In contrast, healthy young adults and children generally mount stronger defense and clear the infection more effectively, so severe disease is less common in those groups.