Fever is a common clinical problem in hospitalized patients. Although the development of fever in a hospitalized patient may be the clinical expression of a community-acquired infection that has completed its incubation period, this chapter focuses on the possible causes of new-onset fever occurring after hospital admission. The reader, however, should keep other diagnoses in mind and inquire about the patient's history of travel, pet and animal exposure, hobbies, sexual activity, dietary preferences and exposures, occupational exposures, recent immunizations, drug (including corticosteroids) and herbal ingestion within the past month, recent exposure to febrile or ill individuals, and other epidemiologic factors such as season of the year.

Hospital-acquired fever may be due to an infectious and/or noninfectious cause, either happening alone or concurrently. An etiology can be identified after appropriate work-up in 72% to 88% of patients. It is not uncommon for length-of-stay and resource utilization to be increased due to the management of the febrile episode.

Not surprisingly, nosocomial infections account for 70% to 75% of causes of fever in hospitalized patients and include bloodstream infections, lower respiratory tract infections, surgical site infections, and urinary tract infections (Table 103.1). Noninfectious causes comprise 25% to 30%. These are usually related to some form of vascular disruption (eg, myocardial infarction, pulmonary embolism), inflammatory (eg, gout) or collagen vascular disease (eg, lupus), endocrine disorder (eg, adrenal insufficiency), malignancy, or drug (Table 103.2).