OBJECTIVES: Longitudinal studies on Swedish respiratory syncytial virus positive (RSV+) patients are lacking. We aim to describe the incidences, laboratory diagnosis, clinical characteristics and health resource utilization (HCRU) of RSV+ patients from Stockholm and Uppsala regions.

METHODS: Patient level data (Jan 2010 - Dec 2021) was extracted from the Healthcare Data Warehouse of Region Stockholm, Electronic Health Records of Stockholm and Uppsala, linked to the Statistic Sweden for health insurance and labor market research. Incidences of RSV+ by age groups, year, RSV season, and region were reported. Comorbidities at time of test being RSV+, incidence of diseases after the RSV+ test, and HCRU including hospitalization were also studied.

RESULTS: Clear seasonality of RSV+ was observed with Dec to Mar associated with highest incidences. Lower RSV+ rates were observed in the season of 2020-2021. Young children (0-5 yr) and elderly (65+ yr) were the most vulnerable to severe RSV disease. Age 65+ was associated with the highest share of comorbidities, including heart failure (36%,34%), coronary artery disease (33%,32%), diabetes (26%,28%), chronic obstructive pulmonary disease (22%,31%) and asthma (20%,23%), for Uppsala and Stockholm, respectively. Within 90 days after RSV+, commonly reported new diseases for the elderly in Uppsala (U) and Stockholm (S) were non-specific respiratory tract infection (22%,27%), non-viral pneumonia (29%, 28%), and secondary pneumonia (19%, 17%). Notably, the elderly had the highest inpatients rates (72% U, 69% S) among the adult age-groups, with mean lengths of hospital stay (LOS) of 10±9.7 (U) and 7.5±8 (S) respectively. Inpatient rates at age 0-5 yr were also high (80% U,79% S), with mean LOS as 7.0±19.1 (U), 5.6±5.3 (S), mainly due to respiratory diseases.

CONCLUSIONS: This is the first population-based cohort in Sweden to delineate the epidemiology of RSV. Elderly and young children have the highest disease burden, calling for research into vaccines and effective care.