Publication date: Jul 15, 2026
Respiratory syncytial virus (RSV) is well recognised as an important contributor to respiratory tract infections (RTIs) in adults in Scotland. However, there is a lack of recognition of the role of human metapneumovirus (hMPV) in RTIs in this population. We compared RSV- and hMPV-associated hospital burden in Scottish adults according to age and comorbidity status before RSV vaccine introduction. We conducted a retrospective cohort study of adults (≥ 18 years) using routinely collected and linked national laboratory, hospital, ICU, and mortality data in Scotland (1 July 2017-30 June 2023). Comorbidity status was defined using UK influenza clinical risk groups mapped from Systematised Nomenclature of Medicine-Clinical Terms (SNOMED-CT) to International Classification of Diseases (ICD)-10 codes. Negative binomial regression was used to estimate adjusted relative hospitalisation rates by virus, age, comorbidity burden (0, 1, > 1), and season. Logistic regression examined associations between virus and long length of stay (LOS), ICU or high-dependency unit (HDU) admission, and 90-day mortality, adjusting for demographic characteristics, number of underlying comorbidities, and COVID-19 pandemic. RSV was associated with higher laboratory-detected hospitalisation rates than hMPV (relative rate ratio 2. 31, 95% confidence interval [CI] 2. 20-2. 43). Hospitalisation rates increased with advancing age, particularly among adults aged ≥ 65 years and with increasing comorbidity burden. Rates varied substantially by season, with marked reductions during the COVID-19 pandemic and a resurgence in 2022/23. Compared with hMPV, RSV was associated with lower odds of prolonged length of stay and ICU/HDU admission, while no substantial difference was observed in 90-day mortality. Across both viruses, increasing age and comorbidity burden were the strongest correlates of adverse clinical outcomes. RSV and hMPV are associated with a substantial hospital burden in adults. Incidence differences likely reflect testing variation. Clinical severity among hospitalised patients was broadly similar between the viruses. Age and multimorbidity were stronger correlates of severe outcomes than virus. The findings highlight the importance of host factors and the need for improved, consistent surveillance to generate robust estimates.
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| Concepts | Keywords |
|---|---|
| Morbidity | |
| Respiratory tract infections | |
| Routine healthcare data | |
| United Kingdom |
Semantics
| Type | Source | Name |
|---|---|---|
| disease | MESH | respiratory tract infections |
| disease | MESH | influenza |
| disease | MESH | ICD |
| disease | MESH | COVID-19 pandemic |
| disease | MESH | Dis |
| disease | MESH | NHS |
| disease | MESH | chronic conditions |
| disease | MESH | morbid obesity |
| disease | MESH | included |
| disease | MESH | infection |
| disease | MESH | nosocomial infections |
| drug | DRUGBANK | Flunarizine |
| disease | MESH | frailty |
| disease | MESH | cystic fibrosis |
| disease | MESH | asthma |
| pathway | KEGG | Asthma |
| disease | MESH | cardiovascular disease |
| drug | DRUGBANK | Pumactant |
| disease | MESH | MSD |
| disease | MESH | PHS |
| pathway | REACTOME | Reproduction |
| disease | MESH | Tam |
| disease | MESH | respiratory syncytial virus infection |
| drug | DRUGBANK | (S)-Des-Me-Ampa |
| disease | MESH | infectious diseases |
| disease | MESH | death |
| drug | DRUGBANK | Coenzyme M |
| drug | DRUGBANK | Saquinavir |