Estimated number and incidence of influenza-associated acute respiratory infection cases in winter 2021/22 in Wanzhou District, China

Abstract

Objectives: Understanding the burden of influenza-associated acute respiratory infection (ARI) and severe ARI (SARI) is crucial for public health decision-making. A population-based study with multiple data sources was conducted to estimate the burden of influenza-associated ARI in Wanzhou District, Chongqing, southern China.

Study design: Population-based surveillance study.

Methods: Active surveillance of ARI was conducted in different levels of health facilities in the Wanzhou District between October 2021 and March 2022. Nasal or throat swabs were collected and tested for influenza viruses in hospital-based surveillance. A health utilisation survey was used to estimate health-seeking behaviour, and all electronic medical records were collected. An epidemiological model was used to estimate the disease burden.

Results: There were an estimated 52,960 influenza-associated ARI (95 % confidence interval [CI]: 39,213-84,891), including 2,529 SARI cases (95 % CI: 1,385-21,712) during winter 2021/22 in the Wanzhou District. The incidence rate for all influenza-associated ARI and SARI was 3,385/100,000 and 162/100,000, respectively. A higher incidence rate of influenza-associated ARI was observed among individuals aged <50 years, while a higher influenza-associated SARI rate was observed in those aged ≥50 years.

Conclusions: Using an epidemiological model with data from multiple sources, this study documented a substantial burden of influenza-associated ARI in the Wanzhou District, highlighting the need for influenza vaccination and providing a possible foundation for public health decision-making.

Keywords: Acute respiratory infection; Disease burden; Incidence rate; Influenza.