Community burden of acute respiratory infections in Shanghai, a longitudinal cohort study in respiratory pathogens, China, 2024-2027.

Purpose: We are conducting a longitudinal cohort study-the Community Burden of Acute Respiratory Infections in Shanghai-to assess age-stratified incidence, healthcare utilisation and risk factors of influenza virus, respiratory syncytial virus (RSV) and SARS-CoV-2 associated acute respiratory infections (ARIs) in Shanghai, China.

Participants: Study participants were enrolled by family doctors in all 47 community health services centres in Pudong New Area District, Shanghai, China. All permanent residents 6 months and older living in Pudong for at least 6 months were eligible for enrolment; residents who planned to leave Pudong for more than 1 month in the first study year were excluded. During enrolment, study staff conducted baseline assessments of sociodemographics, underlying medical conditions, vaccination history and household and self-rated health status. Study participants are being followed for ARIs for 3 years. Nasopharyngeal and oropharyngeal swab specimens are being obtained from suspected ARI cases. Influenza virus, RSV, SARS-CoV-2 and other respiratory pathogens are tested for by multiplex respiratory pathogen real-time quantitative PCR assays. Illness courses and clinical recoveries of ARI cases are assessed through weekly contact with ARI cases for 28 days post ascertainment.

Findings to date: Between 14 October 2024 and 22 November 2024, we enrolled 5387 community residents into the cohort, including 233 children aged from 6 months to 2 years, 278 preschool children aged 3-6 years, 575 school-age children aged 7-18 years, 2150 adults aged 19-64 years and 2151 older adults aged 65+years. All finished baseline assessment and started follow-up. Surveillance of ARI symptoms, collection of specimens and laboratory testing are ongoing.

Future plans: Findings from this study will be used to provide valuable scientific data to inform ongoing control efforts and future pandemic preparedness for respiratory diseases in China. Planned analyses include analysis of annual pathogen-specific incidence by age group and exploration of healthcare seeking behaviour and factors associated with ARIs and severe ARIs. We will also assess transmission dynamics of common respiratory pathogens in a household transmission subcohort.