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Causes and Transmission


Mycoplasma pneumoniae is a bacterium that causes illness by damaging the lining of the respiratory system (throat, lungs, windpipe).


A sick young woman sneezing into a tissue

A person who is sick with M. pneumoniae infection has these bacteria in their nose, throat, windpipe, and lungs. M. pneumoniae is transmitted (spread) from person-to-person when small droplets of water that contain the bacteria get into the air and people breathe them in. People who are sick with M. pneumoniae infection usually spread the disease by coughing or sneezing while in close contact with others, who then breathe in the bacteria.

Most people who are exposed for a short amount of time to someone with M. pneumoniae infection do not become ill. M. pneumoniae infections are known to have long incubation periods (the time between first catching the bacteria from an ill person and development of symptoms). However, it is common for this illness to spread between family members who live together. The incubation period is usually between 1 to 4 weeks.1

Outbreaks occur mostly in crowded settings like schools, college dormitories, military barracks, nursing homes, and hospitals. Transmission of M. pneumoniae to the community has been seen during school-based outbreaks, with most community cases thought to be family members of ill school children.2,3,4


1 Winchell JM. Mycoplasma pneumoniae – A national public health perspective. Curr Pediatr Rev. 2013; doi:10.2174/15733963113099990009.

2 Foy HM, Grayston JT, Kenny GE, Alexander ER, McMahan R. Epidemiology of Mycoplasma pneumoniae infection in families. JAMA. 1966;197:859–66.

3 Walter ND, Grant GB, Bandy U, et al. Community outbreak of Mycoplasma pneumoniae infection: School-based cluster of neurologic disease associated with household transmission of respiratory illness. J Infect Dis. 2008;198:1365–74.

4 CDC. Mycoplasma pneumoniae respiratory illness — two rural counties, West Virginia, 2011. MMWR. 2012;61:834–8.