States. Clusters of CAP cases were found in areas with low-income and black/African American populations. Mortality during hospitalization was 6.5%, corresponding to 102 821 annual deaths in the United States. Mortality at 30 days, 6 months, and 1 year was 13.0%, 23.4%, and 30.6%, respectively. Conclusions. The estimated US burden of CAP is substantial, with >1.5 million unique adults being hospitalized annually, 100 000 deaths occurring during hospitalization, and approximately 1 of 3 patients hospitalized with CAP dying within 1 year. Keywords. community-acquired pneumonia; incidence; epidemiology; mortality. Community-acquired pneumonia (CAP) is the leading cause of infectious disease–related death in the United States, with mortality occurring largely in patients requiring hospitalization [1, 2]. Current assessment of the incidence, epidemiology, and clinical outcomes of patients hospitalized with CAP is important to guide appropriate allocation of resources for prevention, management, and research. CAP is not a reportable infection in the United States; therefore, data regarding the burden of disease are primarily obtained through clinical investigations or through use of administrative datasets [3–5]. These population-based studies are challenging, as researchers must enroll and follow all hospitalized patients with CAP in a clearly defined at-risk population. Considering these challenges, we created the University of Louisville Pneumonia Study Group, a multidisciplinary research collaboration including investigators from University of Louisville Infectious Diseases, Pulmonary Medicine, and Pathology, as well as investigators from the Louisville Department of Public Health and the Kentucky Office of Vital Statistics. The University of Louisville Pneumonia Study Group is an expansion of our already existing clinical research organizational structure initiated in the year 2000 through the Community-Acquired Pneumonia Organization (CAPO) [6] (http://caposite.com/). The objectives of this study were (1) to define the current incidence, epidemiology, and mortality of adult patients hospitalized with CAP in Louisville, Kentucky, and (2) to estimate the burden of CAP in the US adult population. METHODS Study Design and Subjects The University of Louisville Pneumonia Study was a prospective population-based cohort study of all hospitalized adults with CAP who were residents in the city of Louisville, Kentucky, from 1 June 2014 to 31 May 2016. All hospitalized adult patients in Louisville underwent screening for participation in the study. Information on each participating hospital and criteria used to screen all adult hospitalized patients can be found in the Supplementary Materials. MAJOR ARTICLE © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com. DOI: 10.1093/cid/cix647 Received 17 May 2017; editorial decision 7 July 2017; accepted 25 July 2017; published online July 28, 2017. Correspondence: J. A. Ramirez, Division of Infectious Diseases, University of Louisville, 501 E Broadway, Ste 100, Louisville, KY 40202 (j.ramirez@louisville.edu). Clinical Infectious by guest on 04 December 2021 Adults With Pneumonia: Incidence and Mortality • CID 2017:65 (1 December) • 1807 Inclusion Criteria A patient was defined as having CAP when the following 3 criteria were met: (1) presence of a new pulmonary infiltrate on chest radiograph and/or chest computed tomography scan at the time of hospitalization, defined by a board-certified radiologist’s reading; (2) at least 1 of the following: (a) new cough or increased cough or sputum production, (b) fever >37.8°C (100.0°F) or hypothermia 11 000 cells/μL; left shift: >10% band forms/mL; or leukopenia: 1.7 million total annual hospitalizations for CAP in the United States. Two recent studies estimated the incidence of hospitalizations due to CAP in the United States [4, 5]. Griffin et al reported annual rates of hospitalization for CAP using the Agency for Healthcare Research and Quality Nationwide Inpatient Sample (NIS) data, including approximately 20% of US hospitals [4]. The reported incidence of annual