In light of Pope Francis’ latest diagnosis, Dr. Leana Wen explains why older adults are especially at risk for serious disease due to respiratory infections.

Pope Francis was found to have pneumonia in both his lungs Tuesday and his condition remains "complex," the Vatican said in a health update on the 88-year-old pontiff who was hospitalized last week. The big picture: The pope was admitted to Rome's Agostino Gemelli Hospital on Friday with bronchitis symptoms and his treatment was changed after doctors found he had a polymicrobial infection of the respiratory tract.