Pneumonia is a common illness, affecting 1 in 100 people. It is caused by many different types of bacteria, viruses, and other infectious organisms. Each year an estimated 2 million cases occur in the United States. Most cases of pneumonia are mild and easily treated, while some cases are more serious and may result in severe illness and even death.

M. pneumoniae is a common cause of mild pneumonia and usually affects people younger than 40. Various studies suggest that it causes 15-50% of all pneumonia in adults and an even higher percentage of pneumonia in school-aged children.

People at highest risk for mycoplasma pneumonia include those living or working in crowded areas such as schools and homeless shelters, although many people who contract mycoplasma pneumonia have no identifiable risk factor.