Mycoplasma pneumoniae (M. pneumoniae) bacteria can cause respiratory tract infections. They are generally mild but can sometimes progress into something more severe. M. pneumoniae infections are most commonly seen in school-aged children and young adults. Infection may appear more like a cold in children younger than 5 years old. Contact your healthcare provider if experiencing difficulty breathing or concerning symptoms.
Mycoplasma pneumoniae (M. pneumoniae) infection is a mild respiratory illness caused by the bacterium Mycoplasma pneumoniae. People of all ages are at risk for infection, but it is more common in school-aged children and young adults. Outbreaks can occur in crowded environments like military barracks, college dorms, nursing homes and hospitals. Outbreaks in these settings may persist for months.
What are the symptoms of M. pneumoniae?
- Fever
- Cough
- Bronchitis
- Sore throat
- Headache
- Fatigue
- Ear infection
A common outcome of M. pneumoniae infection is pneumonia, sometimes referred to as "walking pneumonia" due to its mild nature and unlikelihood of requiring hospitalization. Approximately 1 out of 3 infected individuals may develop pneumonia.
Younger children may have different symptoms. Instead of chest cold symptoms, children younger than 5 years old may have:
- Diarrhea
- Sneezing
- Sore throat
- Stuffy or runny nose
- Vomiting
- Watery eyes
- Wheezing
Complications
While uncommon, serious complications can occur that require hospital care. M. pneumoniae infections can cause or make the following conditions worse:
- Asthma attacks or new asthma symptoms
- Encephalitis (swelling of the brain)
- Hemolytic anemia (too few red blood cells delivering oxygen)
- Renal dysfunction (kidney problems)
- Serious pneumonia
- Blistering skin disorders like reactive infectious mucocutaneous eruption (RIME)
How long do symptoms last?
Symptoms generally begin 1 to 4 weeks after being exposed to the bacteria and can last anywhere from a few days to more than a month.
How do I know if I have M. pneumoniae?
See your healthcare provider. Your health care provider will review your symptoms and may utilize laboratory testing for a confirmatory diagnosis.
M. pneumoniae is spread through contact with droplets from coughing and sneezing. Transmission usually requires prolonged close contact, making outbreaks in households, schools, and institutions gradual. Diagnosis can be difficult, delaying outbreak reporting and prevention efforts.
While antibiotics may be prescribed, M. pneumoniae infections often resolve on their own, so treatment for mild symptoms may not be necessary.
Other treatments may include, over-the-counter fever reducers and drinking plenty of fluids.
There are currently no vaccines for M. pneumoniae infection. As with any respiratory disease, all people should cover their mouth and nose when coughing or sneezing, and wash their hands frequently. Regularly clean and disinfect surfaces.
CDC Mycoplasma pneumoniae Website
Clinical features of Mycoplasma pneumoniae infection
Cleaning, sanitizing, disinfection
Reporting
Mycoplasma pneumoniae is not a reportable disease in Indiana, therefore data is not widely available. However, outbreaks are reportable to the Respiratory Team within the Infectious Disease Epidemiology and Prevention Division at 317-233-7125.
After a surge in 2024, data suggest Mycoplasma Pneumoniae infections have been decreasing in the United States. However, these infections remain elevated in some U.S. regions.
More Information
Page last reviewed/updated: August 2026
