[Epidemiology of acute lower respiratory tract infections in adults. Role of Chlamydia pneumoniae and Mycoplasma pneumoniae].

INCIDENCE: Mycoplasma pneumoniae and Chlamydia pneumoniae infections cause 15 to 40% of acute pneumonia cases treated by community physicians. This incidence is lower for cases of pneumonia treated in a hospital setting, falling to less than 3% for cases treated in intensive care units. Incidence varies with the geographical area, season, age and patient population.

BRONCHIAL INVOLVEMENT: Mycoplasma pneumoniae and Chlamydia pneumoniae cause 6 to 15% of all cases of acute bronchitis and are the causal agents in approximately 5% of acute episodes in patients with chronic bronchitis.

PATHOGENESIS: Chlamydia pneumoniae and Mycoplasma pneumoniae are general identified as the causal agents on the basis of clinical features, microbiological results and the clinical course. The question of the role of carriers or chronic infection is debated; it most likely has a real effect.