This study estimated the burden of RSV infection in 2019 for Colombia, a middle-income country with universal healthcare coverage. The analysis was stratified by age group, and health affiliation regime (contributory and subsidized). To our knowledge, this is the first study to use this approach to report a national estimate of the RSV burden. The findings of this study are consistent with those presented by Shi et al. (24), who estimated the global number of ARI episodes caused by RSV, reporting that the highest proportion of cases requiring hospital treatment occurs among infants under one year of age. This is likely due to the immaturity of the immune system and a higher risk of respiratory complications due to increased airway resistance, higher metabolic oxygen demand, inefficient respiratory muscles and small functional residual capacity, compared to adults. (25)

For children under five, the incidence in this study aligns with Hall et al. (26), who found higher incidence rates among infants under one year compared to older pediatric age groups. This underscores the need to prioritize prevention in infants under one year as they are highly susceptible to severe complications and death during surge of respiratory infections (27). For adults aged 75 and older, our findings are also consistent with studies highlighting the vulnerability of this population to RSV, particularly those with comorbidities. While the incidence among older adults is lower than in pediatric populations in the current study, RSV can still be a significant cause of morbidity and mortality as demonstrated in our analysis and in several studies (28,29). Recent publication evaluating RSV hospitalization rates in Argentina, Brazil, Chile, and Mexico using a modeling approach estimated rates of 132.8 to 816.5 per 100,000 in adults aged ≥75 years, far greater than what is reported in the current study (30). Additional work should be undertaken to better understand the burden in older adults and adults with comorbidities as many limitations apply in identifying cases of RSV in adults including challenges in diagnostic sensitivity (31–33).

Our study estimated an incidence rate of 61.80 per 1,000 children under one year, similar to the 63.3 per 1,000 reported by Shi et al., based on a meta-analysis of 329 studies estimating the RSV burden in LMICs (24). Our findings on the estimated mortality rate of 3.37 per 100,000 are comparable to those reported by Du et al., who documented a global mortality rate of 4.79 per 100,000 individuals. The study found that RSV mortality rates decline and then rise with age, with higher rates among those over 70 years compared to children under five. This pattern is consistent with our findings, although we report higher mortality rates among infants under one year (27). Gómez et al. (34) estimated RSV-associated hospitalization and mortality burden in adults in five middle-income countries, finding trends similar to ours in four countries (excluding Argentina). This reinforces previous research showing that both young children and the elderly are at higher risk of severe RSV outcomes (26,28,29,35,36).

Our cost analysis revealed a total amount of $682.87 million (95% CI: $281.39 million – $1,084.358 million), or an average cost per patient is $2,579 thousand (95% CI: $1,063 – $4,096) indicating a substantial economic burden. The costs found in the study are consistent with previous studies, such as Rodríguez-Martínez et al. (37), which reported per-patient hospitalization costs in Colombia ranging from $518 in pediatric wards to $2,749 in intensive care units. Buendía et al. (13) also conducted a cost-of-illness study for RSV in infants from Colombia, estimating an annual total cost of $64.44 million (95% CI: $11.09 – $195.72 million) in children under two years. Significant economic burden associated with infant RSV infection was also reported outside of Colombia. Total annual hospitalization costs for infants < 1 year totaled 30.9 MM euros (see figure 1, adding 0 - 5 m and 6 - 11 m for RSV-specific hospitalizations costs) (38). There is a comprehensive approach that includes outpatient and emergency care, offering a broader economic impact perspective.

While the epidemiologic burden of RSV in older adults and adults with comorbidities are increasingly being recognized, the economic burden reported from Latin America region is limited. A study in Argentina reported a mean hospital length of stay of 12 days with 37% requiring intensive care unit admission in adults with confirmed RSV infection, but no costs were reported (39). Based on national data in Spain, a mean cost of RSV hospitalization of €3,870 in adults and a total RSV-attributable hospitalization cost per year of €194 million was recently reported (40). Additional studies in Colombia and Latin America region are needed to better characterize the economic burden of RSV in adults.

This study has several strengths. First, it employs a bottom-up cost-of-illness approach based on individual-level administrative data, enabling a detailed and accurate estimation of the RSV burden from the healthcare system perspective. Second, it provides a comprehensive national analysis across all age groups and both major health insurance regimes (contributory and subsidized), which is rarely addressed in previous studies. Third, unlike prior research that focused primarily on hospitalization costs, this study incorporates costs associated with outpatient, emergency, and intensive care services, offering a broader and more realistic picture of the economic impact of RSV in Colombia.

Nonetheless, some limitations must be acknowledged. The analysis required extrapolation from the contributory regime to the subsidized population due to the lack of individual-level cost data for the latter, which may introduce bias if healthcare-seeking behavior or disease severity differs across regimes. Additionally, the cost analysis was restricted to services covered under the Benefit Plan in Health (PBS), excluding indirect costs such as transportation, productivity losses, and out-of-pocket expenditures, potentially underestimating the total economic burden. Furthermore, the study period precedes the COVID-19 pandemic; thus, results may not reflect current RSV epidemiology or healthcare system dynamics in the post-pandemic context. It is also worth noting that the costs presented in the study are all-cause healthcare utilization and not specific to RSV-related treatment, resulting in a potential overestimation of the costs; however, they are not expected to differ significantly.

Another limitation is the potential under ascertainment of RSV cases, specifically in the adult population. Although PCR testing is systematically performed for all suspected ARI cases in sentinel hospitals, diagnostic accuracy—particularly in adults—is challenged by the lower sensitivity of nasopharyngeal swabs and the need for complementary respiratory specimens or serological tests, as such, case detection is incomplete (31–33). According to recent systematic literature review and modeling studies, the true magnitude of the RSV hospitalization could be 2.2 times what is reported in surveillance studies (41). Moreover, sentinel hospitals only capture patients who seek healthcare services; this causes an exclusion of milder cases, which are more common in this population, and results in potential selection bias. According to Chavez et al. (42), in Bolivia the mean incidence of RSV in adult population from the period 2013-2016 was 77.4 cases for adults aged between 20 and 64 and 607.5 for adults aged 65 and older. The findings from the literature confirm that the RSV incidence rates in adults from the current study are underestimated.