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Mycoplasma pneumoniae (M. pneumoniae) is an "atypical" bacterium (the singular form of bacteria) that causes lung infection. It is a common cause of community-acquired pneumonia (lung infections developed outside of a hospital). M. pneumoniae infections are sometimes referred to as "walking pneumonia." Some experts estimate that between 1 and 10 out of every 50 cases of community-acquired pneumonia in the United States is caused by M. pneumoniae. However, not everyone who is exposed to M. pneumoniae develops pneumonia.

In general, M. pneumoniae infection is a mild illness that is most common in young adults and school-aged children. The most common type of illness caused by these bacteria, especially in children, is tracheobronchitis, commonly called a chest cold. This illness is often seen with other upper respiratory tract symptoms, like a sore throat. Sometimes M. pneumoniae infection can cause pneumonia, a more serious infection of the lungs, which may require treatment or care in a hospital.

Outbreaks of M. pneumoniae occur mostly in crowded environments, like schools, college dormitories, military barracks, and nursing homes, where transmission is possible through airborne droplets from close person-to-person contact. M. pneumoniae infections also frequently spread within households.

How Do You Say That?

Find pronunciation guides below for common words associated with Mycoplasma pneumoniae.

  • Bronchitis — brahn-KITE-uss
  • Mycoplasma — MY-ko-plaz-ma
  • Pneumonia — noo-MOAN-yah
  • Pneumoniae — noo-MOAN-e-a
  • Tracheobronchitis — TRAY-key-o-brahn-KITE-uss