title: Analysis of Risk Factors for Severe Acute Respiratory Infection and Pneumonia and among Adult Patients with Acute Respiratory Illness during 2011-2014 Influenza Seasons in Korea.
abstract: BACKGROUND
  The World Health Organization recommends the surveillance of influenza-like illness (ILI) and severe acute respiratory infection (SARI) to respond effectively to both seasonal influenza epidemics and pandemics. In Korea, the "Hospital-based Influenza Morbidity and Mortality (HIMM)" surveillance system has been operated to monitor ILI and SARI occurrences.
  
  
  METHODS
  A multi-center prospective observational study was conducted. Adult patients with acute respiratory infection (ARI) were enrolled during the 2011-12, 2012-2013, and 2013-2014 influenza seasons at the 10 university hospitals using the HIMM surveillance system. With respect to SARI and pneumonia development, risk profiles were analyzed in patients with ARI in Korea.
  
  
  RESULTS
  A total of 5,459 cases were eligible for this analysis. Among 5,459 cases with ARI, 2,887 cases (52.9%) were identified that they had influenza infection. Among enrolled cases, 750 cases belonged to the SARI group, while 4,709 cases belonged to the non-SARI group. With respect to pneumonia development, 317 cases were accompanied by pneumonia, and 5,142 cases were not. Multivariate analyses revealed that the following factors were associated with an increased risk of SARI: Old age (≥65 years) (odds ratio [OR] 2.69, 95% confidence interval [CI] 2.2-3.32), chronic heart disease (CHD) (OR 2.24, 95% CI 1.68-2.98), cerebrovascular disease (CVD) (OR 1.49, 95% CI 1.05-2.10), chronic obstructive pulmonary disease (COPD) (OR 2.34, 95% CI 1.48-3.69), asthma (OR 2.33, 95% CI 1.62-3.36), chronic kidney disease (CKD) (OR 2.62, 95% CI 1.73-3.99), chronic liver disease (OR 1.71, 95% CI 1.04-2.81), and autoimmune diseases (OR 2.53, 1.57-4.08). Multivariate analyses revealed that the following factors were independent risk factors for pneumonia development: Old age (≥65 years) (OR 5.71, 95% CI 4.10-7.94), CHD (OR 1.54, 95% CI 1.07-2.22), COPD (OR 2.34, 95% CI 1.48-3.69), asthma (OR 2.33, 95% CI 1.62-3.36), CKD (OR 2.62, 95% CI 1.73-3.99), immunocompromised conditions (OR 3.12, 95% CI 1.47-6.62), and autoimmune diseases (OR 3.35, 95% CI 1.79-6.27). The risk of SARI and pneumonia was increased by the number of concurrent chronic medical conditions.
  
  
  CONCLUSIONS
  The risk of SARI and pneumonia development among adult patient with ARI was significantly increased by the presence or number of concurrent chronic medical conditions in Korea.
authors.affiliation: Department of Internal Medicine, Konyang University College of Medicine, Daejeon, Korea.
authors.forename: Seong Hui
authors.identifier: http://orcid.org/0000-0003-3698-0007
authors.initials: SH
authors.lastname: Kang
authors.affiliation: Department of Internal Medicine, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
authors.forename: Hee Jin
authors.identifier: http://orcid.org/0000-0002-2739-0948
authors.initials: HJ
authors.lastname: Cheong
authors.affiliation: Department of Internal Medicine, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
authors.forename: Joon Young
authors.identifier: http://orcid.org/0000-0002-0148-7194
authors.initials: JY
authors.lastname: Song
authors.affiliation: Department of Internal Medicine, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
authors.forename: Ji Yun
authors.identifier: http://orcid.org/0000-0001-8541-5704
authors.initials: JY
authors.lastname: Noh
authors.affiliation: Department of Internal Medicine, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
authors.forename: Ji Ho
authors.identifier: http://orcid.org/0000-0002-6197-1789
authors.initials: JH
authors.lastname: Jeon
authors.affiliation: Department of Internal Medicine, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
authors.forename: Min Joo
authors.identifier: http://orcid.org/0000-0002-2739-0948
authors.initials: MJ
authors.lastname: Choi
authors.affiliation: Department of Internal Medicine, Kangnam Sacred Heart Hospital, Hallym University School of Medicine, Seoul, Korea.
authors.forename: Jacob
authors.identifier: http://orcid.org/0000-0002-7041-065X
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Kangnam Sacred Heart Hospital, Hallym University School of Medicine, Seoul, Korea.
authors.forename: Yu Bin
authors.identifier: http://orcid.org/0000-0001-5183-1996
authors.initials: YB
authors.lastname: Seo
authors.affiliation: Department of Internal Medicine, Inha University College of Medicine, Incheon, Korea.
authors.forename: Jin Soo
authors.identifier: http://orcid.org/0000-0001-7862-5519
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, St. Vincent's Hospital, School of Medicine, The Catholic University of Korea, Suwon, Korea.
authors.forename: Seong Heon
authors.initials: SH
authors.lastname: Wie
authors.affiliation: Department of Internal Medicine, Chungbuk National University College of Medicine, Cheongju, Korea.
authors.forename: Hye Won
authors.initials: HW
authors.lastname: Jeong
authors.affiliation: Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: Young Keun
authors.initials: YK
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Chonnam National University School of Medicine, Kwangju, Korea.
authors.forename: Kyung Hwa
authors.initials: KH
authors.lastname: Park
authors.affiliation: Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea.
authors.forename: Shin Woo
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Eun Joo
authors.identifier: http://orcid.org/0000-0001-8058-7136
authors.initials: EJ
authors.lastname: Jeong
authors.affiliation: Department of Internal Medicine, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Sun Hee
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
authors.forename: Won Suk
authors.identifier: http://orcid.org/0000-0001-5874-4764
authors.initials: WS
authors.lastname: Choi
authors.affiliation: Department of Internal Medicine, Guro Hospital, Korea University College of Medicine, Seoul, Korea.|Transgovernmental Enterprise for Pandemic Influenza in Korea, Seoul, Korea. wjkim@korea.ac.kr.
authors.forename: Woo Joo
authors.identifier: http://orcid.org/0000-0002-4546-3880
authors.initials: WJ
authors.lastname: Kim
keywords: Complication; Hospitalization; Influenza; Pneumonia; Risk factors