Clinical features and outcome of 2009 influenza A (H1N1) virus infections in children with malignant diseases: a case-control study.

BACKGROUND: The impact of the novel 2009 influenza A (H1N1) (2009 H1N1) virus in children with malignant diseases under therapy is not well known. OBJECTIVE: To analyze the clinical features and outcome in children with anticancer therapy infected with the 2009 H1N1 virus. PATIENTS AND METHODS: Descriptive, case-control study. Between May and July 2009, 24 cases of 2009 (H1N1) virus infections in children with malignant diseases were registered and 48 control cases of similar patients infected with common influenza A virus (IA) diagnosed between 2006 and 2008 were selected. RESULTS: Median age for cases was 72 months and for controls was 83 months (P ≥ 0.05). Children with IA showed neutropenia more frequently (52% vs. 17%), longer period of time with illness before diagnosis (3 d vs. 1.7 d), higher rate of earlier medical consultation (69% vs. 25%), and more antibiotic therapy courses (54% vs. 4%; P ≤ 0.05) than patients with 2009 H1N1 virus. Children infected with this virus presented hypoxemia more frequently (42% vs. 8%) and higher rates of intensive care unit hospitalizations (29% vs. 2%; P ≤ 0.05). Three children with 2009 H1N1 virus and 1 in the control group died. CONCLUSIONS: Children infected with 2009 H1N1 virus presented more morbidity and mortality than patients infected with seasonal IA virus.