The organism has 2 properties that seem to correlate well with its pathogenicity in humans. The first is a selective affinity for respiratory epithelial cells and, secondly, the ability of the organism to produce hydrogen peroxide, which is thought to be responsible for much of the initial cell disruption in the respiratory tract and damage to erythrocyte membranes. Although mycoplasmal pneumonia can occur at any time of the year, outbreaks tend to occur in the fall months. The incubation period averages 3 weeks, in contrast to influenza and other viral pneumonias, which generally incubate over a few days. Epidemics of mycoplasmal pneumonia tend to occur every 4-8 years in the general population and tend to be more frequent within closed populations, such as in the military and prisons.
Incidence is higher in males than females.
Mycoplasmal pneumonia is a disease of gradual and insidious onset over several days to weeks. Sore chest and tracheal tenderness is a result of the protracted cough. Pleuritic chest pain is rare. A nontoxic general appearance Erythematous tympanic membranes or bullous myringitis may occur. Various exanthems have been noted.