Pathogenic analysis on children cases of influenza among inpatients and outpatients in Fangshan district of Beijing, 2015-2017

Abstract

Objective To analyze the pathogenic characteristics of child cases of influenza among inpatients and outpatients in Fangshan district of Beijing during 2015-2017. Methods A total of 2 816 throat swab samples of child influenza-like illness (ILI) (0-14 years old) and from sever acute respiratory infection (SARI) cases in sentinel hospitals in Fangshan from 2015 to 2017 were collected. Real time RT-PCR was used to detect nucleic acids of influenza virus. The pathogenic characteristics of child cases of influenza among inpatients and outpatients were analyzed by descriptive epidemiological methods. Results From 2015 to 2017, 224 cases were tested positive with the positive rate of 7.95% (224/2 816), of which the positive rate of influenza B/Victoria (33.93%, 76/224) were the highest, followed by influenza A (H1N1) (26.34%, 59/224) and other influenza viruses, e.g. influenza A (H3N2) and influenza B/Yamagata. Dominant strain was different in flu season of each year. The positive detection rate of influenza in ILI cases of outpatients (9.90%, 125/1 263) was higher than than that in SARI cases of inpatients (6.37%, 99/1 553). The difference was statistically significant (x2=11.80, P=0.001). The positive rate of influenza in ILI cases of outpatients was the highest among children of 7-14 years old (18.14%, 39/215) while the rate in SARI cases was the highest among children of 4-6 years old (8.91%, 36/404). Conclusions Dominant strain was different in the flu season of each year in Fangshan district, Beijing. The positive rate of influenza in ILI was slightly higher than that in SARI cases. Children over 4 years old were vulnerable to influenza. Key words: Children; Influenza; Influenza-like illness; Sever acute respiratory infection