title: Male predominance of pneumonia and hospitalization in pandemic influenza A (H1N1) 2009 infection.
abstract: BACKGROUND
  Pandemic influenza A (H1N1) disproportionately affects different age groups. The purpose of the current study was to describe the age and gender difference of pandemic influenza A (H1N1) cases that lead to pneumonia, hospitalization or ICU admission.
  
  
  METHODS
  Data were collected retrospectively between May 2009 and December 2009. All of the diagnoses of H1N1 were confirmed by real-time reverse-transcription polymerase chain reaction (RT-PCR).
  
  
  RESULTS
  During the study period there were 3402 cases of RT-PCR positive H1N1, among which 1812 were males and 1626 were adults (> 15 years of age). 6% (206/3402) of patients required hospitalization, 3.6% (122/3402) had infiltrates on chest radiographs, and 0.70% (24/3402) were admitted to intensive care unit (ICU). The overall fatality rate was 0.1% (4/3402). The rate of hospitalization was sharply increased in patients ≥ 50 years of age especially in male. Out of 122 pneumonia patients, 68.8% (84 patients) were male. Among the patients admitted to the ICU, 70.8% (17 patients) were male. Approximately 1 of 10 H1N1-infected patients admitted to the ICU were ≥ 70 years of age.
  
  
  CONCLUSIONS
  Among the confirmed cases of H1N1, the ICU admission rate was < 1% and the case fatality rate was 0.1%. Male had a significantly higher rate of pneumonia and hospital admission. These findings should be taken into consideration when developing vaccination and treatment strategies.
authors: Department of Internal Medicine, Dongsan Hospital, Keimyung University School of Medicine, Daegu, Republic of Korea. wichoi@dsmc.or.kr.
authors: Won-Il
authors: WI
authors: Choi
authors: Byung Hak
authors: BH
authors: Rho
authors: Mi-Young
authors: MY
authors: Lee