The epidemiologic feature of viral infection in the children with acute lower respi-ratory tract infections in Shanghai

Objective To understand the epidemiologic feature of viral infection in the children with acute lower respiratory tract infections in Shanghai. Methods From October 2002 to April 2004, a total of 4 534 hospitalized children with acute respiratory tract infection were studied. Nasopharyngeal aspirates were screened for virus by direct immunofluorescent (DIF) assay. Results Virus was identified in 1 837 patients (~40.2% ), 1 630 (~88.7% ) of them were under 3 years of age. The most prevalent was respiratory syncytial viruses (RSV) (831, ~45.2% ), followed by influenza A (330, 18.0%), parainfluenza 1, 3 (232, ~12.6% ),influenza B (201, ~10.9% ), parainfluenza 2 (114, ~6.2% ),adenovirus (96, ~5.2% ) and mixed viral infection (33, ~1.8% ). The children with RSV infection was younger (median age 5 months, range ~0.1 -156 months) than those with other viral infection. The seasonal change of RSV was more obvious. The peak of RSV appeared from January to February in 2003 and 2004. Influenza A and B also had a small peak from October to December in 2002. Positive rate of virus was 53.4% in children with bronchiolitis. RSV accounted for 79.5%, followed by influenza A (~13.5% ),parainfluenza 2 (~2.6% ) and adenovirus (~2.6% ). The prevalence of viral infection in children with pneumonia, bronchitis, laryngotracheobronchitis, asthmatic bronchitis and asthma were ~41.3% , ~35.3% , ~40.3% , ~42.6% and ~36.5% respectively. Conclusions The respiratory viruses are still a main cause of lower respiratory tract infections in children, especially in infants and younger children, in Shanghai. RSV and influenza A was the most common viruses in these years. Both RSV and influenza had their own seasonality in epidemic. RSV remains the main pathogen of bronchiolitis, while influenza A was prominent in the patients with ‘wheezing’ symptom.