Epidemiology, trends and determinants of influenza and SARS-CoV-2 positivity among severe acute respiratory infection patients in Cambodia, 2020–2024: a hospital-based retrospective cross-sectional surveillance data analysis
Khemrin Pong, Hayputhik Long, Sokly Mom, Sophanith Ung, Darapheak Chau, Sengdoeurn Yi, Piseth Keam, Heng Seng, Ly SovannObjective
To describe the epidemiological pattern, temporal trends of influenza and SARS-CoV-2, and determinants of severe acute respiratory infection (SARI)-confirmed positivity among patients hospitalised with SARI in Cambodia.
Design
A hospital-based retrospective cross-sectional surveillance data analysis using national sentinel SARI surveillance data collected from 2020 to 2024.
Setting
Nine SARI sentinel hospitals are located across Cambodia.
Participants
A total of 16 739 hospitalised patients who met the SARI case definition.
Measure
SARI-confirmed positivity defines all SARI cases with laboratory-confirmed influenza or SARS-CoV-2 infections as the main outcome measure. Descriptive and bivariate analyses were performed, followed by multivariate logistic regression to identify factors associated with SARI-confirmed positivity.
Results
Among 16 739 SARI cases, median age in years was 16 (IQR=59), with 54.6% being male; 13.5% were laboratory-confirmed for influenza or SARS-CoV-2. High mortality rate in 2021. A(H3N2) dominated in 2020, followed by widespread SARS-CoV-2 circulation in 2021. In 2022, SARS-CoV-2 co-circulated with A(H3N2) and influenza B (Victoria). A(H1N1)pdm became the predominant strain in 2023 as SARS-CoV-2 and A(H3N2) declined. In 2024, A(H3N2) again led circulation, with B(Victoria) and SARS-CoV-2 also detected. Sporadic A(H5N1) cases began appearing in late 2023. Multivariable analysis indicated higher odds of SARI-confirmed positivity among children aged 5–14 years (adjusted OR (aOR)=1.85; 95% CI 1.47 to 2.31) and adults 50–64 years (aOR=1.36; 95% CI 1.15 to 1.60) compared with adults 25–49 years, during the rainy season (aOR=2.09; 95% CI 1.89 to 2.32) and among patients in Phnom Penh compared with other regions (p<0.001). Influenza detection markedly increased from 2022 to 2024 following the decline observed during the COVID-19 pandemic.
Conclusion
These results indicate that there was an increase in SARI trends over the periods and the changing influenza subtypes circulating each year, along with a high mortality rate during the Delta variant COVID-19 pandemic in Cambodia. Age, region, year and season were significant factors associated with SARI-confirmed positivity. Targeted interventions and preventive measures should be prioritised for specific high-risk groups.