title: Asthma and severity of the 2009 novel H1N1 influenza: a case-control study.
abstract: OBJECTIVE
  Previous studies reported that the most common chronic condition found among hospitalized patients due to the novel 2009 H1N1 influenza was asthma. However, these studies did not include a concurrent control group. Thus, we investigated the association of asthma status and severity of H1N1 influenza in adults.
  
  
  METHODS
  The study was designed as a multi-site case-control study. Cases were patients who had positive PCR for H1N1 influenza and were admitted to the ICU or general ward with a diagnosis of H1N1 influenza from 1 January 2009 to 31 December 2009. Controls were patients who had positive PCR for H1N1 influenza, but were not admitted to hospitals.
  
  
  RESULTS
  There were 91 H1N1 cases admitted to either ICU (n = 41) or general hospital ward (n = 50), and 56 controls who met the matching criteria were available. Of the 91 cases, the mean age was 47.3 years, 59% were female, and 38% had comorbid conditions. Of the 91 cases, 12 (13%) had asthma. Stratified analysis by comorbid conditions showed that among those without any comorbid conditions, 8 of 56 cases (14%) and 2 of 49 controls (4%) had asthma, (OR: 3.92, 95% CI: 0.79-19.42, p = 0.095) whereas, among the 39 subjects with one or more comorbid conditions, one of 7 controls (14%) had asthma and 4 of 35 (11%) cases had asthma (p = 0.83).
  
  
  CONCLUSIONS
  Asthma may be associated with severity of H1N1 influenza among those without any non-asthma comorbid conditions. However, the limited sample size did not allow this study to fully establish statistical significance. We still recommend asthmatics as a priority group for influenza vaccination and treatment.
authors.affiliation: Department of Internal Medicine, Hallym University Medical Center, Kandong Sacred Heart Hospital , Seoul , Korea .
authors.forename: Yong Bum
authors.initials: YB
authors.lastname: Park
authors.forename: Changhwan
authors.initials: C
authors.lastname: Kim
authors.forename: Yong Il
authors.initials: YI
authors.lastname: Hwang
authors.forename: Chang Lyul
authors.initials: CL
authors.lastname: Lee
authors.forename: Won-Yeon
authors.initials: WY
authors.lastname: Lee
authors.forename: Hye Yun
authors.initials: HY
authors.lastname: Park
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Heo
authors.forename: Hyun Kyung
authors.initials: HK
authors.lastname: Lee
authors.forename: Jae Hwa
authors.initials: JH
authors.lastname: Cho
authors.forename: Yong Soo
authors.initials: YS
authors.lastname: Kwon
authors.forename: Ji Ye
authors.initials: JY
authors.lastname: Jung
authors.forename: Young J
authors.initials: YJ
authors.lastname: Juhn
authors.forename: Barbara P
authors.initials: BP
authors.lastname: Yawn
authors.forename: Kent
authors.initials: K
authors.lastname: Bailey
authors.forename: Kwang Ha
authors.initials: KH
authors.lastname: Yoo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001249:Asthma / Q000453:epidemiology*; D016022:Case-Control Studies; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D056910:Republic of Korea / Q000453:epidemiology; D012720:Severity of Illness Index; D055815:Young Adult