Chlamydia pneumoniae is a type of bacteria that can cause respiratory tract infections, such as pneumonia. C. pneumoniae is one cause of community-acquired pneumonia or lung infections developed outside of a healthcare setting. However, not everyone exposed to C. pneumoniae will develop pneumonia.

In general, Chlamydia pneumoniae infection is a mild illness that most commonly causes an upper respiratory tract infection. These upper respiratory tract infections can include a sore throat or an ear or sinus infection. Common symptoms include:

• Runny or stuffy nose
• Fatigue (feeling tired)
• Low-grade fever
• Hoarseness or loss of voice
• Sore throat
• Slowly worsening cough that can last for weeks or months
• Headache

C. pneumoniae can also cause lower respiratory tract infections like bronchitis (inflammation or swelling of the airways that carry air to the lungs) and pneumonia (lung infection). Some reports say that people with pneumonia caused by C. pneumoniae are more likely to have laryngitis (inflammation of the voice box) compared to people with other types of bacterial pneumonia.

It can take 3 to 4 weeks for symptoms to appear after someone has been exposed to the bacteria. Symptoms can also continue for several weeks after they start.