Epidemiological characteristics of influenza among the elderlyin Heilongjiang Province / 预防医学

ABSTRACT

Objective @#To investigate the epidemiological characteristics of influenza among the elderly in Heilongjiang Province from 2017 to 2021 (April 2017 to March 2022), so as to provide insights into influenza control among the elderly.@*Methods @#The data pertaining to surveillance of patients with influenza-like illness (ILI) at ages of 60 years and older in Heilongjiang Province from 2017 to 2021 were retrieved from Chinese Influenza Surveillance Information Management, and the temporal distribution of ILI cases and the results of influenza virus tests were descriptively analyzed. @*Results @#Totally 26 908 ILI cases at ages of 60 years and older were reported in Heilongjiang Province from 2017 to 2021, with an ILI prevalence rate of 0.17%. The prevalence of ILI appeared a tendency towards a rise in Heilongjiang Province from 2017 to 2021 (χ2trend=268.554, P<0.001), and the epidemic peaked in the 3rd to 7th weeks of 2019 and 2020. The overall positive rate of influenza virus was 6.80%, and the positive rate of influenza virus showed a tendency towards a decline from 2017 to 2021 (χ2trend=425.268, P<0.001). Influenza A (H1N1) pdm09 (46.82%) and A (H3N2) (22.79%), as well as influenza B virus lineages B/Victoria (12.11%) and B/Yamagata (18.28%) were predominant types, which changes among the study period. The detection of influenza virus-positive samples peaked from December to March of the next year, and a high positive rate of influenza virus was detected in Hegang (12.35%), Heihe (11.47%) and Daqing cities (11.07%). There was no significant correlation between the prevalence of ILI and the positive rate of influenza virus in Heilongjiang Province from 2017 to 2021 (rs=-0.800, P=0.104).@*Conclusions@# The prevalence of ILI appeared a tendency towards a rise among the elderly at ages of 60 years and older in Heilongjiang Province from 2017 to 2021, and the epidemic peaked in winter and spring. Influenza A (H1N1) pdm09, A (H3N2), B/Victoria, B/Yamagata were alternately prevalent and there was no obvious correlation between ILI prevalence and the positive rate of influenza virus.