Shanghai yufang yixue (Oct 2022)
Surveillance and analysis of influenza-like illness cases in a sentinel hospital in Nantong from 2014 to 2021
Abstract
ObjectiveTo analyze the surveillance results of influenza-like illness （ILI） cases in a sentinel hospital in Nantong from 2014 to 2021 and to understand the seasonal and etiological characteristics of influenza.MethodsThe routine ILI case information in a sentinel hospital in Nantong from 2014 to 2021 was collected from China Influenza Surveillance Information system， and the surveillance results were described and analyzed.ResultsA total of 64 110 ILI cases were reported in the hospital from 2014 to 2021， and accounted for 3.93% of outpatient and emergency visits. ILI is mainly concentrated in children under 15 years old， accounting for 55.39% of the total ILI cases. ILI% roughly showed two epidemic peaks in spring and winter. A total of 8 639 nasopharyngeal swab samples of ILI cases were collected during 2014‒2021， of which 838 were influenza positive， with an average positive rate of 10.01% （3.27%‒16.75%）. The epidemic strains varied from year to year and in different age groups. In 2014 and 2015， H3N2 influenza was the epidemic strain； in 2016 and 2017， H3N2 influenza and B-Victoria influenza were the co-epidemic strains； in 2018， H1N1 influenza was the epidemic strain； and in 2019‒2021， B Victoria influenza was the epidemic strain. The epidemic strain in 0‒4 years old， 15‒24 years old， 25‒59 years old and >60 years old was H3N2， and the epidemic strain in 5‒14 years old was B Victoria. There was a significant difference in the positive rate between different gender groups （χ2=7.364， P=0.006）.ConclusionInfluenza often occurs in winter and spring in a sentinel hospital in Nantong. Influenza subtypes are prevalent alternately in different age groups and different years. We need to closely monitor the etiology of influenza virus in Nantong to provide a basis for influenza prevention and control.
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