Surveillance, assessment and detection of influenza-associated respiratory infections in a high HIV burden setting in Lusaka, Zambia: A protocol for a cross-sectional surveillance study

<ns3:p>Background Respiratory viral infections including influenza, respiratory syncytial virus (RSV), and COVID-19 contribute substantially to morbidity and mortality across age groups. Influenza alone is associated with up to 650,000 deaths and approximately 5 million annual hospitalizations globally. Although well documented in high-income countries, the epidemiology of respiratory viral infections remains limited in low-middle income countries, specifically southern Africa, including Zambia, where respiratory tract infections rank among the top causes of morbidity and mortality. While these infections frequently present mildly and may exhibit a self-limiting course, early diagnosis in routine care settings and strong surveillance systems are essential for transmission prevention, syndromic management of acute infection, improved diagnostic stewardship and emerging pathogen detection. This study aims to characterise the influenza burden and other viral infections among adults with influenza-like illness (ILI) in Zambian outpatient clinics while evaluating the performance of a breath-based sample collection mask compared with nasopharyngeal swabbing for viral pathogen diagnosis. Methods This observational study is being conducted at two primary healthcare facilities, in Lusaka, Zambia, recruiting adults aged ≥18 years presenting with ILI for 2–7 days. Participants undergo clinical evaluation, chest x-ray, and nasopharyngeal swab sampling. Participants also wear facemasks for 30 minutes for breath-aerosol collection. Samples will be analysed using multiplex assays. They also complete a researcher-administered acceptability questionnaire and a daily symptom diary for two weeks. The primary outcome is influenza A/B prevalence; secondary outcomes include RSV & SARS-CoV-2 prevalence, seasonality, co-infection, clinical outcomes, diagnostic accuracy, and acceptability of facemask versus nasopharyngeal sampling. Heidelberg University, University of Zambia, and Zambia National Health Research Authority granted ethical approval. Discussion This study will strengthen epidemiological data on respiratory viral infections, and support evidence for local influenza vaccine implementation. It may inform future adoption of facemask-based sampling as a novel, preferable, potentially self-administered method for respiratory pathogen detection. Trial registration The study was retrospectively registered on www.clinicaltrials.gov on 19 June 2025 with number NCT07030075.</ns3:p>