Chlamydial pneumonia

C. pneumoniae is a bacterium that can infect the upper or lower respiratory tract and cause bronchitis or pneumonia; the organism damages the lining of the respiratory tract, including the throat, windpipe, and lungs ^[1].

Common presentations include fatigue, headache, hoarseness, low-grade fever, runny nose, sore throat, and a slowly worsening cough, with symptoms often developing 3–4 weeks after exposure and persisting for several weeks; relative to other bacterial pneumonias, laryngitis is more frequent, serious complications are uncommon, and some infected individuals remain asymptomatic ^[1].

First infection most often occurs in school-aged children or young adults, whereas reinfection and more severe disease are more common in older adults; outbreaks can occur in crowded settings, and overall occurrence reflects the bacterium's wide capacity to cause upper and lower respiratory tract infections ^[1].

C. pneumoniae spreads when infected individuals cough or sneeze respiratory droplets that reach the mouths or noses of others, and contaminated hands or surfaces can also transmit the bacteria ^[1].

Covering coughs and sneezes and regular hand hygiene help reduce spread; there is no vaccine to prevent C. pneumoniae infection, and healthcare providers generally do not prescribe antibiotics after exposure for prophylaxis ^[1].

1. 1US Centers for Disease Control and Prevention. About Chlamydia pneumoniae Infection | C. pneumoniae | CDC [Internet]. cited 3 Sept 2026.Available from: https://www.cdc.gov/cpneumoniae/about/index.html