A descriptive and prospective research with the aim of identifying the viral etiology and a number of related factors based on the diagnostic criteria, severe classification of the Royal Children's Hospital of Melbourne, 2017; virus is determined by in vitro molecular amplification technique (Realtime PCR) for Adenovirus, Rhinovirus and rapid test for detection of antigens for RSV, influenza A, and influenza B. Results showed that there were 134 patients with bronchiolitis, of which patients with severe bronchitis accounted for 17.2%; the rate of children under 12 months old accounts for 80.6%; The male / female ratio is 2.19 / 1; Virus were identified in 70.9% of cases: RSV 47.8%, Rhinovirus 33.0%, Adenovirus 13.1%, influenza A 6.1%, influenza B 0%, co-infection rates of 2 types of virus was 14.7% and RSV infection was a factor associated with severe and moderate bronchitis requiring hospitalization.