Etiology and epidemiology of respiratory infections in community-based influenza-like illness during the COVID-19 pandemic, Vientiane, Lao People's Democratic Republic

Objectives: Respiratory infections pose an ongoing global public health burden, with multiple viral and bacterial etiologies. This study aimed to characterize the etiology of influenza-like illness (ILI) during the COVID-19 pandemic in a community cohort in Vientiane, Lao People's Democratic Republic (Lao PDR). Methods: From September 2021 to April 2022, 6300 individuals from 999 households in 25 villages were enrolled in a prospective surveillance study. Oropharyngeal swabs were collected from ILI cases and tested for SARS-CoV-2 using reverse transcription-polymerase chain reaction, and for 21 additional respiratory pathogens using a multiplex panel. Results: Among 462 samples analyzed, 360 (77.92%) were positive for at least one pathogen, including 338 viral and 79 bacterial infections. SARS-CoV-2 was predominant (67.53%), followed by Staphylococcus aureus (12.55%), human rhinovirus (6.93%), and Streptococcus pneumoniae (5.41%). Seasonal viruses, such as influenza A/B, respiratory syncytial virus, human parainfluenza virus, and human metapneumovirus were notably absent. Co-infections occurred in 21.21% of cases, with lower rates among SARS-CoV-2positive individuals. Conclusions: These findings highlight the dominance of SARS-CoV-2 and the suppression of typical seasonal viruses, likely due to public health measures and viral interference. The results emphasize the importance of multiplex, community-level surveillance to understand respiratory pathogen dynamics and to strengthen preparedness in resource-limited settings.