Epidemiological analysis of influenza virus type A in hospitalized children with respiratory tract infection in Suzhou area from 2006 to 2015

Objective To analyze the epidemiological characteristics of influenza virus type A (FluA) in children with respiratory tract infection, and to provide scientific basis for clinical diagnosis and treatment. Methods Sputum specimens of 35 529 cases of hospitalized children with respiratory tract diseases from January 2006 to December 2015 in Suzhou were collected. FluA was detected by direct immunofluorescence and the FluA detection result was analyzed. Groups were compared with chi-square test. Results The FluA infection rate was 1.60% in 35 529 children. The FluA infection rate of boys was 1.58%, and the rate of girls was 1.63%. There was no obvious statistically significant difference in sex (χ2=0.139, P=0.709). The FluA infection rates of children at the age of less than 1 year, less than 3 years, less than 7 years and older than 7 years respectively were 1.12%, 2.49%, 1.78%, and 1.24%; there was significant differences among these result (χ2=75.401, P=0.000). The FluA infection rates in spring, summer, autumn and winter respectively were 0.88%, 1.44%, 1.32%, 2.70%. The rates in four seasons had significant difference (χ2=105.432, P=0.000). The FluA infection rate was the highest in winter and the lowest in spring. The FluA infection rate was 6.55% in the autumn of 2008, which was the highest in the recent ten years. Conclusions FluA is one of the important pathogens of respiratory tract infection in children in Suzhou area. The infection rate of infant is higher and the epidemic peak is in winter. The FluA infection has obvious epidemic season and year. The FluA infection rates in Suzhou area are 0.64%-3.49%, and there was no outbreak in the recent ten years. Key words: Influenza virus type A; Respiratory tract infection; Epidemiology; Children