Influenza surveillance in Ezhou city, Hubei Province, 2016-2021

ABSTRACT

ObjectiveTo analyze the influenza surveillance data in Ezhou City, Hubei Province from 2016 to 2021, determine the epidemiological characteristics and etiological trend of influenza like illness (ILI), and to provide scientific evidence for influenza prevention and control. MethodsThe ILI surveillance data were reported by Ezhou influenza sentinel hospitals and etiological examination results were collected by network laboratory. Influenza surveillance data from 2016 to 2021 were analyzed. ResultsFrom 2016 to 2021, the percentage of ILI visits (ILI%) in Ezhou city was 2.81% and increased over years. Majority (55.55%) of ILI cases were 0-4 years. A total of 7 716 ILI samples were examined from 2016 to 2021, of which 1 467 tested positive with a positive rate of 19.01%. Influenza A H1N1 was mainly concentrated in January-April, A H3N2 mainly in August-December, B Victoria mainly in April-July and December-March, and B Yamagata mainly in December-February. Influenza network laboratory isolated influenza virus from the 1 467 positive samples by using MDCK cells and SPF chicken embryos. The overall isolation rate was 32.78%, which was 26.93% by MDCK cells and 5.86% by SPF chicken embryos. From 2016 to 2021, a total of 13 ILI outbreaks were reported in Ezhou City. Temporally, the outbreaks mainly occurred in winter and spring. Spatially, they were mainly in primary schools, middle schools and kindergartens. ConclusionThe winter and spring are the key time period of influenza prevention and control in Ezhou City, as they are susceptible to influenza outbreaks. Children aged 0-14 are the key population of prevention and control. Diverse subtypes of influenza virus alternate by years, which warrants continually strengthening monitoring. Additionally, certain countermeasures against COVID-19 may be recommended in the prevention and control of influenza.