title: Community-Acquired Pneumonia Requiring Hospitalization among U.S. Adults.
abstract: BACKGROUND
  Community-acquired pneumonia is a leading infectious cause of hospitalization and death among U.S. adults. Incidence estimates of pneumonia confirmed radiographically and with the use of current laboratory diagnostic tests are needed.
  
  
  METHODS
  We conducted active population-based surveillance for community-acquired pneumonia requiring hospitalization among adults 18 years of age or older in five hospitals in Chicago and Nashville. Patients with recent hospitalization or severe immunosuppression were excluded. Blood, urine, and respiratory specimens were systematically collected for culture, serologic testing, antigen detection, and molecular diagnostic testing. Study radiologists independently reviewed chest radiographs. We calculated population-based incidence rates of community-acquired pneumonia requiring hospitalization according to age and pathogen.
  
  
  RESULTS
  From January 2010 through June 2012, we enrolled 2488 of 3634 eligible adults (68%). Among 2320 adults with radiographic evidence of pneumonia (93%), the median age of the patients was 57 years (interquartile range, 46 to 71); 498 patients (21%) required intensive care, and 52 (2%) died. Among 2259 patients who had radiographic evidence of pneumonia and specimens available for both bacterial and viral testing, a pathogen was detected in 853 (38%): one or more viruses in 530 (23%), bacteria in 247 (11%), bacterial and viral pathogens in 59 (3%), and a fungal or mycobacterial pathogen in 17 (1%). The most common pathogens were human rhinovirus (in 9% of patients), influenza virus (in 6%), and Streptococcus pneumoniae (in 5%). The annual incidence of pneumonia was 24.8 cases (95% confidence interval, 23.5 to 26.1) per 10,000 adults, with the highest rates among adults 65 to 79 years of age (63.0 cases per 10,000 adults) and those 80 years of age or older (164.3 cases per 10,000 adults). For each pathogen, the incidence increased with age.
  
  
  CONCLUSIONS
  The incidence of community-acquired pneumonia requiring hospitalization was highest among the oldest adults. Despite current diagnostic tests, no pathogen was detected in the majority of patients. Respiratory viruses were detected more frequently than bacteria. (Funded by the Influenza Division of the National Center for Immunizations and Respiratory Diseases.).
authors.affiliation: From the Centers for Disease Control and Prevention, Atlanta (S.J., A.M.B., C.R., M.L., S.L., J.M.W., J.M.K., D.E., E.S., L.A.H., L.F.); Vanderbilt University School of Medicine (W.H.S., C.G.G., J.D.C., F.C., D.J.W., Y.Z., K.M.E.) and University of Tennessee Health Science Center-Saint Thomas Health (C.T.), Nashville, and Le Bonheur Children's Hospital (S.R.A., J.A.M.), University of Tennessee Health Science Center (S.R.A., J.A.M.), and St. Jude Children's Research Hospital (J.A.M.), Memphis - all in Tennessee; Northwestern University Feinberg School of Medicine (R.G.W., E.J.A., D.M.C., C.Q., E.M.H., H.K.D., G.W.W.), John H. Stroger, Jr., Hospital of Cook County (S.F.), and Rush University Medical Center (R.B.) - all in Chicago; University of Utah Health Sciences Center, Salt Lake City (K.A., A.T.P.); and University of Western Australia, Perth (G.W.W.).
authors.forename: Seema
authors.initials: S
authors.lastname: Jain
authors.forename: Wesley H
authors.initials: WH
authors.lastname: Self
authors.forename: Richard G
authors.initials: RG
authors.lastname: Wunderink
authors.forename: Sherene
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authors.lastname: Fakhran
authors.forename: Robert
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authors.lastname: Balk
authors.forename: Anna M
authors.initials: AM
authors.lastname: Bramley
authors.forename: Carrie
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authors.lastname: Reed
authors.forename: Carlos G
authors.initials: CG
authors.lastname: Grijalva
authors.forename: Evan J
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authors.lastname: Anderson
authors.forename: D Mark
authors.initials: DM
authors.lastname: Courtney
authors.forename: James D
authors.initials: JD
authors.lastname: Chappell
authors.forename: Chao
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authors.lastname: Qi
authors.forename: Eric M
authors.initials: EM
authors.lastname: Hart
authors.forename: Frank
authors.initials: F
authors.lastname: Carroll
authors.forename: Christopher
authors.initials: C
authors.lastname: Trabue
authors.forename: Helen K
authors.initials: HK
authors.lastname: Donnelly
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Williams
authors.forename: Yuwei
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authors.lastname: Zhu
authors.forename: Sandra R
authors.initials: SR
authors.lastname: Arnold
authors.forename: Krow
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authors.lastname: Ampofo
authors.forename: Grant W
authors.initials: GW
authors.lastname: Waterer
authors.forename: Min
authors.initials: M
authors.lastname: Levine
authors.forename: Stephen
authors.initials: S
authors.lastname: Lindstrom
authors.forename: Jonas M
authors.initials: JM
authors.lastname: Winchell
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Katz
authors.forename: Dean
authors.initials: D
authors.lastname: Erdman
authors.forename: Eileen
authors.initials: E
authors.lastname: Schneider
authors.forename: Lauri A
authors.initials: LA
authors.lastname: Hicks
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: McCullers
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Pavia
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Edwards
authors.forename: Lyn
authors.initials: L
authors.lastname: Finelli
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002641:Chicago / Q000453:epidemiology; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000145:classification / Q000453:epidemiology* / Q000382:microbiology; D011159:Population Surveillance; D011859:Radiography; D012307:Risk Factors; D012621:Seasons; D012720:Severity of Illness Index; D013714:Tennessee / Q000453:epidemiology; D055815:Young Adult