OBJECTIVETo analyze the viral etiologies of hospitalized pneumonia patients aged less than five years in six provinces during 2009-2012, and to describe the seasonality of the detected viral etiologies.

METHODSEight hospitals were selected in six provinces from a national acute respiratory infection surveillance network. Demographic information, clinical history and physical examination, and laboratory testing results of the enrolled hospitalized patients aged less than five years with pneumonia, including respiratory syncytial virus (RSV), human influenza virus, adenoviruses (ADV), human parainfluenza virus (PIV), human metapneumovirus (hMPV), human coronavirus (hCoV)and human bocavirus (hBoV) were analyzed. The viral etiology spectrum of the enrolled patients was analyzed by age-group, year, and seasonality of the detected viral etiologies were described.

RESULTS4 508 hospitalized children less than five years old, with pneumonia from 8 hospitals were included, and 2 688 (59.6%) patients were positive for at least one viral etiology. The most frequent detected virus was RSV (21.3%), followed by PIV (7.1%) and influenza (5.2%), hBoV (3.8%), ADV(3.6%) and hMPV(2.6%). The lowest positive rates in hCoV(1.1%). RSV, influenza, PIV, hBoV and hMPV all showed the nature of seasonality.

CONCLUSIONRSV was a most common viral etiology in the hospitalized young children less than 5 years of age with pneumonia. Prevention measures should be conducted to decrease its severe impact to the young infants and children in China.