OBJECTIVETo analyze the clinical characteristics of severely and critically ill children with 2009 influenza A (H1N1) infection.

METHODClinical data of 150 cases with 2009 influenza A (H1N1) virus infection confirmed with the use of a real-time polymerase-chain-reaction assay on nasopharyngeal swab specimens were analyzed.

RESULTAmong 150 severely and critically ill children with 2009 influenza A (H1N1) virus infection, 103 were male, 47 were female; the median age was 5 years, 81(55%) were 5 years of age or older; 21 (14%) had underlying chronic diseases. The most common presenting symptoms were fever (95%), cough (89%), vomiting (23%), wheezing (19%), abdominal pain (16%), lethargy (7%), seizures (6%), myalgia (6%), and diarrhea (6%). The common laboratory abnormalities were increased or decreased white blood cells counts (40%), elevated of CRP (33%), LDH (29%), CK (25%) and AST (19%). Clinical complications included pneumonia (65%), encephalopathy (12%), myocarditis (5%), encephalitis (1%) and myositis (1%). All patients had received antibiotics before admission or on admission; 73% of patients had received oseltamivir treatment, 23% of patients had received corticosteroids; 32 (21%) were admitted to an ICU, 13 patients were intubated and mechanically ventilated. Fourteen patients with dyspnea who were irresponsive to the treatment experienced bronchoalveolar lavage with flexible bronchoscopy, and the branching bronchial casts were removed in 5 patients. Totally 145 (97%) patients were discharged, five (3%) died, three previously healthy patients died from severe encephalopathy, one patient died from ARDS, one previously healthy patient died from secondary fungal meningitis.

CONCLUSIONSeverely and critically ill children with 2009 influenza A (H1N1) virus infection may occur mainly in older children without underlying chronic disease. The clinical spectrum and laboratory abnormality of the patients can have a wide range. Neurologic complications may be common and severe encephalopathy can lead to death in previously healthy children. Early use of bronchoalveolar lavage with flexible bronchoscopy may reduce death associated with pulmonary complications.