Epidemiology of community-acquired pneumonia in adults: a population-based study

In this prospective study, the authors assessed the incidence, aetiology, and outcome of patients with community-acquired pneumonia in the general population. From December 1993 to November 1995, a study was performed in a mixed residential-industrial urban population of the "Maresme" region in Barcelona, Spain. All subjects > or =14 yrs of age (annual average population size 74,368 inhabitants) with clinically suspected community-acquired pneumonia were registered. All cases were re-evaluated by chest radiographs on the 5th day of illness and at monthly intervals until complete recovery. Urine and blood samples were obtained for culture and antigen detection. When lower respiratory tract secretions were obtained, these were also cultured. There were 241 patients with community-acquired pneumonia, with an annual incidence rate of 1.62 cases (95% confidence interval, 1.42-1.82) per 1,000 inhabitants. Incidence rates increased by age groups and were higher in males than in females. Of 232 patients with aetiological data, 104 had an identifiable aetiology. A total of 114 pathogens were found (single pathogen 94, two pathogens 10). There were 81 episodes of bacterial infection and 33 of viral infection. The most common pathogens were Streptococcus pneumoniae, Chlamydia pneumoniae, and influenza A and B viruses. No case of Hantavirus infection was found. The rate of hospital admission was 61.4% with a mean+/-SD length of 11.7+/-10.1 days, a mean period of 23.0+/-14.3 days inactivity, and an overall mortality rate of 5%. The high rate of hospital admission, prolonged stay in hospital, and long period of inactivity all continue to constitute a social and health care burden of community-acquired pneumonia.