M. pneumoniae is usually spread by inhalation of aerosolized particles or inhalation of the contents of the oropharnyx, of an infected individual.  The contents of the oropharnyx are often ejected into the air as a result of a sneeze or cough.  After inhalation of the bacterium, it travels to the respiratory epithelium found in the lungs.  Another, less common path of

infection is through open wounds in other areas of the body.  After M. pneumoniae enters the blood stream it travels to the lungs, its preferred habitat and multiplies.

            Since M. pneumoniae is transmitted through the air, close contact with infected individuals is required for transmission.  This is why living and working in crowded conditions is the largest risk factor for disease transmission.  Prison, military, and other closed populations are especially at risk because of extremely tight living conditions.  M. pneumoniae infection occurs in individuals under 40 years old and is most common in before 20 years old.  However, infections are uncommon in those under four years old, likely due to limited contact with large numbers of people.