What is community-acquired pneumonia (CAP)?

Pneumonia is an infection that causes lung parenchymal inflammation. It is one of the leading infective causes of morbidity and mortality worldwideWorld Health Organization (WHO), 2021.

Community-acquired pneumonia (CAP) is pneumonia that develops in patients in the community, or in patients who have been in hospital for less than 48 hours. However, pneumonia that develops in a patient who has been discharged within the previous 7 days from a hospital admission of longer than 48 hours should be managed as for hospital-acquired pneumonia (HAP)Kalil, 2016National Institute for Health and Care Excellence (NICE), 2019Torres, 2017US Food and Drug Administration (FDA), 2020.

Most cases of pneumonia develop due to aspiration of bacteria from the oropharynx; this is true of all pneumonia, not just aspiration pneumonia. Antibiotic regimens for CAP in these guidelines can be used for initial treatment of aspiration pneumonia in patients from the community – see Management of a patient who has had an aspiration event.

This topic covers the management of CAP in adults. Management of CAP in children, CAP in residents of an aged-care facility who are being treated in the facility, HAP and ventilator-associated pneumonia (VAP) is covered elsewhere; to find the right pneumonia topic in these guidelines, see Finding the right pneumonia topic in these guidelines.

Once the pathogen is known, see Directed therapy for pneumonia.