Abstract: Objective To investigate the pathogens in children with acute respiratory infection (ARI) and epidemiological characteristics in Changzhou region. Methods The sera were collected from 2 259 children with ARI, and IgM antibodies against 9 kinds of pathogenic microorganisms, including Iegionella pneumophila type 1 (LP-1), mycoplasma pneumonia (MP), Q fever rickettsia (QFR), chlamydia pneumonia (CP), adenovirus (ADV), respiratory syncytial virus (RSV), influenza A virus (FluA), influenza B virus (FluB) and parainfluenza virus (PIV), were detected by indirect immuno-fluorescence assay. The results were analyzed statistically. Results Among 2 259 children with ARI , 856 cases were detected positively, which accounted for 37.9% . Of the 856 cases, there were 601 cases of infection with unique microorganism (70.2%). MP infection was predominant, and the positive rate was 43.6%. The positive rates of FluB, RSV and PIV were 11.4%, 6.3% and 5.3%, respectively. There were 29.8% (255/856) mixed infection, and the main mixed infection was MP+FluB (8.4%), followed by MP+PIV (5.8%), MP+RSV (2.9%), MP+LP-1 (2.4%) and MP+PIV+RSV (1.4%). Among the 856 positive cases, the percentages of MP were 34.4%, 64.0%, 51.5% and 54.6% respectively in <1 year old, 1- 4 years old, 5-8 years old and > 8 years old groups.The highest positive rate was noted in the 1-4 years old group (χ²=18.127, P<0.01). The positive rates of RSV, FluB and PIV had no significant difference in every age group (P>0.05). The rate of children infected with ARI was higher in autumn and winter, which accounted for 11.8% and 13.6%, respectively. Conclusions MP are major pathogens among children with ARI and complicated with virus infection in Changzhou region. The 1- 4 years old children as susceptible populations occur in the autumn and winter, and the therapy of macrolide antibiotics in combination with ribavirin is effective.

Key words: Epidemiology, Acute respiratory infection, Child, Indirect immuno-fluorescence assay