Influenza surveillance among children in Songjiang District of Shanghai, 2014-2018

ObjectiveTo investigate the epidemiological characteristics of influenza in Songjiang District, Shanghai during 2014-2018, and to provide scientific evidence for the prevention of influenza.

MethodsWe collected the data including influenza-like illness(ILI)report, etiological examination and influenza outbreak in Songjiang, and further characterized the epidemic of influenza using descriptive statistics.

ResultsData from the sentinel hospital-based surveillance system showed two peaks of influenza incidence in winter and summer in Songjiang, in which the winter peak was more significant. The largest proportion of ILI was the age group 0-4 years(57.90%). The proportion of being positive for influenza nucleic acid was 18.44%. All principal types of influenza were prevalent in Songjiang with a certain pattern of alternative circulation, in which influenza B virus accounted for 41.18% among all the types, followed by seasonal H3(36.95%)and H1N1(21.98%). A total of 650 influenza strains were isolated. The total proportion of isolation was 67.08%, which fluctuated by year with a peak of 79.37% in 2016. Of all the 27 outbreaks of influenza, 88.89% of them were identified in primary and middle schools and 70.37% occurred in December.

ConclusionDifferent subtypes of influenza viruses were prevalent alternatively in Songjiang during 2014-2018. The etiological results and influenza outbreaks are generally in consistent with ILI report. It warrants necessary prevention in primary and middle schools in epidemic seasons of influenza.