Mycoplasma pneumoniae is a bacterium that causes respiratory tract infections. Many infections are mild and improve without specific treatment, but the bacterium can also cause tracheobronchitis and pneumonia, sometimes called walking pneumonia.
Symptoms
Symptoms often develop gradually and may include:
- persistent or slowly worsening cough
- fever or chills
- headache
- sore throat
- fatigue and feeling unwell
- shortness of breath when pneumonia develops
Children younger than 5 may have different symptoms, including a runny or stuffy nose, wheezing, vomiting or diarrhea. Symptoms can overlap with viral respiratory infections and other causes of pneumonia.
How it spreads
The bacteria spread mainly through respiratory droplets produced by coughing and sneezing. Infection is more likely after prolonged close contact, and outbreaks can occur in households, schools, colleges, hospitals, long-term care facilities and other crowded settings. Symptoms usually begin about one to four weeks after exposure.
There is no vaccine. Handwashing and covering coughs and sneezes can help reduce spread. Preventive antibiotics are not routinely recommended simply because someone has been exposed.
Diagnosis
A healthcare professional may assess symptoms, breathing and oxygen levels and may order a chest X-ray when pneumonia is suspected. Laboratory testing is not necessary for every mild infection. When specific testing is needed, molecular tests such as nucleic acid amplification tests are generally preferred because they can provide timely and accurate results.
Treatment
Most mild M. pneumoniae infections are self-limiting. Pneumonia caused by the bacterium is commonly treated with an appropriate antibiotic. Because Mycoplasma bacteria lack a cell wall, penicillin and other beta-lactam antibiotics do not work against them.
Antibiotic choice depends on factors such as age, pregnancy, illness severity and local resistance patterns. Macrolide resistance varies geographically. Antibiotics should be used only when clinically indicated and taken exactly as prescribed.
When to seek medical help
Arrange medical assessment for persistent or worsening respiratory symptoms, wheezing, significant shortness of breath, or illness in someone at increased risk of severe infection, including people with underlying lung disease or a weakened immune system.
Seek urgent medical help for severe difficulty breathing, blue or gray lips or skin, confusion, collapse, severe chest pain, or rapidly worsening illness. Use your local emergency medical service when symptoms are severe or life-threatening.
Possible complications
Serious complications are uncommon but can include severe pneumonia, worsening asthma, encephalitis, hemolytic anemia, kidney problems and severe mucocutaneous reactions. New neurological symptoms, a severe blistering rash or marked deterioration require prompt medical assessment.
Related topics
Sources and Further Reading
- CDC: About Mycoplasma pneumoniae Infection
- CDC: Clinical Care of Mycoplasma pneumoniae Infection
- CDC: Laboratory Testing for Mycoplasma pneumoniae
Last reviewed: 4 September 2026