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Signs and Symptoms

A grandmother reading to her sick grandson

In general, Mycoplasma pneumoniae infection is a mild illness with symptoms that appear and get worse over a period of 1 to 4 weeks. This bacterium can cause several types of infections. Pneumonia (lung infection) may be the most serious type of M. pneumoniae infection, but not everyone will develop pneumonia. It is estimated that only 1 out of every 3 people who get ill from M. pneumoniae actually get pneumonia.

The most common type of illness, especially in children, is tracheobronchitis, commonly known as chest cold. This chest cold often comes with:

  • Sore throat
  • Fatigue (being tired)
  • Fever
  • Slowly worsening cough that can last for weeks or months
  • Headache

Children younger than 5 years old often do not run a fever when they have M. pneumoniae infection. Instead they may have signs that appear more like a cold than pneumonia. They sometimes wheeze, vomit, or have diarrhea.