History and Disease Patterns


As early as the 1930’s, scientists were reporting pneumonias that were “atypical” compared to characteristics seen in “typical” pneumonias. Patients with atypical pneumonia tended to be not as sick, have symptoms for longer, and not respond to some antibiotics used for treating “typical” pneumonia. In 1944, scientists discovered the agent that cause “atypical” pneumonia, later named as Mycoplasma pneumoniae. They first thought it was a virus or fungus so they chose the name “mycoplasma,” which is Greek for “fungus-formed.” Eventually, scientists learned that it is a bacterium with many unique characteristics. For example, it does not have a rigid cell wall, which affects the types of antibiotics that work well against it. It is also the smallest organism capable of living and reproducing on its own. Smaller germs, like viruses, have to live and reproduce inside cells.

Disease Patterns

M. pneumoniae infections are common in the United States. The number of infections varies over time, with peaks of disease every 3 to 7 years. An estimated 2 million cases of M. pneumoniae infections occur each year in the United States.1,2 However, many infections are not diagnosed, so the actual number is likely higher. This illness can happen any time during the year but may be more common in summer and early fall.3


1 Marston BJ, Plouffe JF, File Jr TM, et al. Incidence of community-acquired pneumonia requiring hospitalization. Results of a population-based active surveillance study in Ohio. The Community-Based Pneumoniae Incidence Study Groupexternal icon. Arch Intern Med. 1997;157:1709–18.

2Porath A, Schlaeffer F, Lieberman D. The epidemiology of community-acquired pneumonia among hospitalized adultsexternal icon. J Infect. 1997;34:41–8.

3 Winchell JM. Mycoplasma pneumoniae – A national public health perspectiveexternal icon. Curr Pediatr Rev. 2013;9(4):324–33.