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Open Access Research article

Male predominance of pneumonia and hospitalization in pandemic influenza A (H1N1) 2009 infection

Won-Il Choi1*, Byung Hak Rho2 and Mi-Young Lee3

Author Affiliations

1 Department of Internal Medicine, Dongsan Hospital, Keimyung University School of Medicine, Daegu, Republic of Korea

2 Department of Diagnostic Radiology, Dongsan Hospital, Keimyung University School of Medicine, Daegu, Republic of Korea

3 Department of Preventive Medicine, Dongsan Hospital, Keimyung University School of Medicine, Daegu, Republic of Korea

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BMC Research Notes 2011, 4:351  doi:10.1186/1756-0500-4-351

Published: 10 September 2011

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.

Keywords:
Influenza; H1N1; Gender; Pneumonia; Admission