Accepted for/Published in: Interactive Journal of Medical Research
Date Submitted: Mar 17, 2023
Date Accepted: Aug 28, 2024
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
Changes in the epidemiological features of influenza after the COVID-19 pandemic: updated influenza activity for China, the USA, and Australia
ABSTRACT
Background:
There has been a global decrease in seasonal influenza activity since the onset of the COVID-19 pandemic.
Objective:
We aimed to describe influenza activity during the 2021/2022 season and compare it to the trends from 2012-2023. We also explored the influence of social and public health prevention measures during the COVID-19 pandemic on influenza activity.
Methods:
We obtained influenza data from January 1, 2012, to February 5, 2023, from publicly available platforms for China, the USA, and Australia. Mitigation measures were evaluated based on the stringency index, which is a composite index developed by the Balavatnik School of Government, University of Oxford. The influenza activities were compared among these three countries. General additive model (GAM) was used to assess the correlation between the stringency index and the influenza positivity rate, and determination coefficient（R2） was calculated.
Results:
Influenza activity remained low in the USA, and Australia during the 2021/2022 season. However, it was increased in the USA with the positive rate of 26.19% in the 49th week of 2022. During the 2021/2022 season, influenza activity significantly increased compared with the previous year in mainland China, with peak positivity rates of 27.55% in the second week of 2022, and with two seasonal influenza activity peaks during winter and summer, respectively. Uniquely, after the COVID-19 pandemic, the dominant influenza virus genotype in China was type-B (Victoria), especially during the 2021/2022 season, and accounted for >99% of all cases. In all these three areas, influenza virus type B (Yamagata) was not detected after COVID-19 pandemic. There was significant correlation between the stringency index and influenza positivity rate among these countries for both influenza type A and type B. The R2 was 0.467(p<0.05) for influenza A and 0.129(p<0.05) for influenza B in China. The correlation between stringency index and influenza activity were relatively stronger in the USA (R2 (A)= 0.701, p < 0.05, R2 (B)= 0.978, p < 0.05). The correlations between the stringency index and the influenza positivity rate in Australia, for influenza type A was 0.512(p<0.05) and for type B was 0.413(p<0.05).
Conclusions:
Influenza activity was increased gradually since 2021 in these areas. Although mitigation measures for COVID-19 showed correlations with influenza activity in the three areas, which was mainly driven by the early stage of the pandemic. During late 2021 and 2022, the mitigation management for COVID-19 did not the only influence factor for influenza activity, and other effectors emerged.
Citation
