INTRODUCTIONSingapore had its first case of pandemic influenza A (H1N1) 2009 on 26 May 2009. As of 3 August 2009, 440 children with confirmed H1N1were admitted to KK Women's and Children's Hospital (KKH).

MATERIALS AND METHODSThis is a retrospective case control study of children admitted from 26 May 2009 to 19 July 2009 with H1N1infection. Cases and controls were first differentiated by whether they were complicated or non-complicated in nature, and subsequently analysed with regards to possible independent risk factors.

RESULTSWe analysed 143 admitted children; 48 cases and 95 controls (1: 2 ratio). Significant comorbidity was found in 20.3% (n = 29) of patients with the majority having asthma (n = 18, 12.6 %) followed by obesity (n = 7, 4.9%). Binary logistic regression analysis showed risk factors for complicated disease were comorbidity (adjusted OR 6.0, 95% CI, 2.5 to 14.6, P < 0.0001) and age <2 years (adjusted OR 9.8, 95% CI, 2.4 to 40, P = 0.001). Age less than 5 years was not found to be a risk factor.

CONCLUSIONIn the early stages of an evolving influenza epidemic when oseltamivir stocks are low, oseltamivir treatment for influenza can be streamlined and offered to those at highest risk who are under 2 years old or have significant comorbidity to prevent complicated disease.

Adolescent ; Age Factors ; Antiviral Agents ; therapeutic use ; Asthma ; complications ; Bronchitis ; complications ; Case-Control Studies ; Child ; Child, Preschool ; Cohort Studies ; Female ; Fluid Therapy ; Gastritis ; virology ; Gastroenteritis ; virology ; Humans ; Infant ; Influenza A Virus, H1N1 Subtype ; isolation & purification ; Influenza, Human ; complications ; Male ; Obesity ; complications ; Oseltamivir ; therapeutic use ; Pneumonia, Bacterial ; complications ; Retrospective Studies ; Risk Factors ; Seizures ; complications ; Singapore