RSV Disease Burden in Adults in Emerging Market Countries, a Systematic Review and Modelling Analysis
Sebastien Kenmoe, Bhanu Wahi-Singh, Pia Wahi-Singh, Caihua Liang, Julia Regazzini Spinardi, Reiko Sato, Shuyu Deng, Elizabeth Begier, You Li, Harish NairAbstract
Background
Most previous studies on adult respiratory syncytial virus (RSV) burden focus on high-income settings (HIC). With the recent approval of RSV vaccines for adults, extending epidemiological understanding to emerging market countries (EMC) is critical for informing prevention strategies. We aimed to characterize the burden of RSV among adults ≥18 years in EMC.
Methods
We conducted a systematic review (PROSEPRO: CRD420251137828) to identify studies reporting estimates of RSV burden from any care setting in adults>18 years in EMC. For each individual study included, we followed a two-step statistical approach to adjust for RSV case under-ascertainment related to the use of clinical specimen and diagnostic test. Random-effects meta-analysis was conducted to estimate RSV incidence rate, proportion positive, hospitalisation, and mortality burden.
Findings
We included 70 studies of which the majority were from China (30/70) and PCR was the predominant diagnostic method (59/70). Adjusted RSV disease incidence rate (approximately 2.5 times higher than unadjusted) ranged from 2,544 (95% CI 1,352-4,787) per 100,000 in adults aged 18-49 years to 2,392 (1,618-3,534) in adults ≥65 years after accounting for clinical sampling and diagnostic testing. Adjusted hospitalisation rates increased with age, from 20 (8-51) per 100,000 in 18-49 years to 74 (3-2,027) in adults ≥65 years, representing an approximate 2.5-fold increase after adjustment. The adjusted RSV proportion positive was relatively stable, ranging from 1.8% (0.4-8.5) to 9.7% (6.3-14.6), regardless of settings or clinical case definitions. The unadjusted in-hospital case fatality ratio (hCFR) was 6.0% (2.9-11.9) in adults ≥65 years vs 3.1 (2.0-5.0) in those 18-49 years. Among hospitalized RSV-positive adults, 95.8% (84.2-99.0) had at least one comorbidity, most commonly hypertension, diabetes, and COPD.
Conclusion
The estimated incidence and proportion positive of RSV disease in EMC is substantially lower than HIC. Narrow case definitions requiring fever, less sensitive testing such as direct fluorescent antibody testing, reduced healthcare access, and incomplete surveillance may be contributing to these lower estimates. In-hospital CFR are comparable to or higher than in HIC.