AUTHOR=Lin Chun-Pang , Dorigatti Ilaria , Tsui Kwok-Leung , Xie Min , Ling Man-Ho , Yuan Hsiang-Yu TITLE=Impact of early phase COVID-19 precautionary behaviors on seasonal influenza in Hong Kong: A time-series modeling approach JOURNAL=Frontiers in Public Health VOLUME=10 YEAR=2022 URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2022.992697 DOI=10.3389/fpubh.2022.992697 ISSN=2296-2565 ABSTRACT=Background

Before major non-pharmaceutical interventions were implemented, seasonal incidence of influenza in Hong Kong showed a rapid and unexpected reduction immediately following the early spread of COVID-19 in mainland China in January 2020. This decline was presumably associated with precautionary behavioral changes (e.g., wearing face masks and avoiding crowded places). Knowing their effectiveness on the transmissibility of seasonal influenza can inform future influenza prevention strategies.

Methods

We estimated the effective reproduction number (Rt) of seasonal influenza in 2019/20 winter using a time-series susceptible-infectious-recovered (TS-SIR) model with a Bayesian inference by integrated nested Laplace approximation (INLA). After taking account of changes in underreporting and herd immunity, the individual effects of the behavioral changes were quantified.

Findings

The model-estimated mean Rt reduced from 1.29 (95%CI, 1.27–1.32) to 0.73 (95%CI, 0.73–0.74) after the COVID-19 community spread began. Wearing face masks protected 17.4% of people (95%CI, 16.3–18.3%) from infections, having about half of the effect as avoiding crowded places (44.1%, 95%CI, 43.5–44.7%). Within the current model, if more than 85% of people had adopted both behaviors, the initial Rt could have been less than 1.

Conclusion

Our model results indicate that wearing face masks and avoiding crowded places could have potentially significant suppressive impacts on influenza.