Fast Facts

  • Mycoplasma pneumoniae is a small bacterium that infects the lungs and other parts of the respiratory tract. People can spread these bacteria to others by coughing or sneezing.
  • Pneumonia caused by M. pneumoniae is considered an atypical bacterial pneumonia because:
    • It tends to cause milder illness but symptoms tend to last longer
    • It can appear differently on an x-ray
    • The antibiotics commonly used in the past to treat bacterial pneumonia did not work against it
  • Symptoms of illness caused by M. pneumoniae usually start gradually. It can take someone between 1 to 4 weeks to get sick after they are exposed to the bacteria.
  • Most M. pneumoniae infections are mild and get better on their own without treatment, but serious complications can occur.
  • An estimated 2 million cases of M. pneumoniae infections occur each year in the United States.1,2 The true number is unknown and likely underestimated.
  • M. pneumoniae is the second most common cause of pneumonia-related hospitalization in adults with community-acquired pneumonia (lung infections developed outside of a hospital).2
  • M. pneumoniae may cause between 1 and 10 in every 50 cases of community-acquired pneumonia in the United States.1,3,4,5,6


1 Marston BJ, Plouffe JF, File Jr TM, et al. Incidence of community-acquired pneumonia requiring hospitalization. Results of a population-based active surveillance study in Ohio. The Community-Based Pneumonia Incidence Study GroupExternal. Arch Intern Med. 1997;157:1709–18.

2 Porath A, Schlaeffer F, Lieberman D. The epidemiology of community-acquired pneumonia among hospitalized adultsExternal. J Infect. 1997;34:41–8.

3 Foy HM. Infections caused by Mycoplasma pneumoniae and possible carrier state in different populations of patientsExternal. Clin Infect Dis. 1993;17:S37–46.

4 Foy HM, Kenny GE, McMahan R, Mansy AM, Grayston JT. Mycoplasma pneumoniae pneumonia in an urban area. Five years of surveillanceExternal. JAMA. 1970;214:1666–72.

5 Mundy LM, Oldach D, Auwaerter PG, et al. Implications for macrolide treatment in community-acquired pneumonia. Hopkins CAP TeamExternal. Chest. 1998;113:1201–6.

6 Michelow IC, Olsen K, Lozano J, et al. Epidemiology and clinical characteristics of community-acquired pneumonia in hospitalized childrenExternal. Pediatrics. 2004;113:701–7.