OBJECTIVETo compare the clinical features and co-infection between pneumonia caused by influenza virus A (IVA) and pneumonia caused by influenza virus B (IVB) among children.

METHODSA total of 165 children with pneumonia caused by influenza virus (IV) were included in the study. These subjects were divided into IVA(n=71) and IVB pneumonia groups (n=94) according to the subtypes of IV. The IVA pneumonia group was further divided into simple infection (n=14) and co-infection subgroups (n=57), and the IVB pneumonia group was also further divided into simple infection (n=27) and co-infection subgroups (n=67). Co-infection rate and pathogen spectrum were analysed in children with IV pneumonia.

RESULTSThe IVB pneumonia group had significantly increased mean age of onset and significantly prolonged mean duration of fever compared with the IVA pneumonia group (P<0.05). Co-infection rate among children with IV pneumonia was 75.2%, who were co-infected with bacteria (44.2%), Mycoplasma pneumoniae (MP, 21.8%) and other viruses (45.5%). Respiratory syncytial virus (RSV) was most common in children co-infected viruses (89% ). The rate of co-infection with RSV was significantly higher in the IVA pneumonia group than in the IVB pneumonia group. There were no significant differences in age, length of hospital stay, duration of fever, percentage of neutrophils, prealbumin, C-reactive protein, alanine aminotransferase, and creatine kinase-MB between the simple infection and co-infection subgroups of each group.

CONCLUSIONSChildren with IVB pneumonia have prolonged duration of fever and increased age of onset compared with those with IVA pneumonia. Co-infection rate is high among children with IV pneumonia, who may be co-infected with bacteria, viruses and MP. Co-infection with RSV is more common in children with IVA pneumonia. It is difficult to identify the presense of co-infection using clinical indices.