Mycoplasma pneumoniae infection is relatively common in clinical settings, but what exactly is Mycoplasma pneumoniae? Mycoplasma pneumoniae is different from ordinary bacteria and also from viruses. It is smaller than bacteria but larger than viruses, and it exists between bacteria and viruses as the smallest microorganism that can live independently. After infecting humans, Mycoplasma pneumoniae often causes bronchial pneumonia, with symptoms such as fever and cough. After treatment with sensitive antibiotics, most cases can recover within two to three weeks.