Respiratory Syncytial Virus Hospitalizations Among Adults in Thailand: A Nationwide Retrospective Observational Study (RSV‐HAT)

BACKGROUND: Respiratory syncytial virus (RSV) is a major cause of acute respiratory infection (ARI) in adults, especially older individuals, yet data on burden in Thailand are limited. This study aimed to describe clinical characteristics and mortality risk factors of RSV-related hospitalizations in Thai adults. METHODS: We conducted a retrospective analysis using Thailand's national hospital database, including adults aged ≥ 18 years hospitalized with RSV-associated ARIs between June 2016 and September 2024, identified using ICD-10 codes J12.1, J20.5, J21.0, and B97.4. Demographics, case fatality ratio, and healthcare resource utilization were assessed. Multivariable logistic regression identified predictors of in-hospital mortality, and Kaplan-Meier analysis estimated 60-day overall survival by age and comorbidity status. RESULTS: Among 1595 RSV-related hospitalizations, the mean age was 66.5 years; 72.0% were aged ≥60 years and 78.4% had ≥ 1 comorbidity, most commonly hypertension, diabetes, chronic respiratory disease, and chronic heart disease. The median length of stay (LOS) was 7 days, 17.3% required oxygen therapy, and 8.2% received invasive mechanical ventilation (IMV). The in-hospital mortality was 9.53%. Mortality was independently associated with age ≥ 75 years (mOR 1.83, p = 0.019), LOS ≥ 7 days (1.95, p = 0.001), IMV (2.94, p < 0.001), pneumonia (4.10, p < 0.001), and acute myocardial infarction (3.05, p = 0.005). The 60-day survival rate was 88.2%, declining to 84.0% in patients aged ≥ 75 years (p < 0.001) and 87.1% in those with comorbidities versus 92.2% in those without (p = 0.013). CONCLUSIONS: RSV causes substantial morbidity and mortality in Thai adults, especially those aged ≥ 75 years and with chronic comorbidities, underscoring the need for strengthened RSV surveillance and prevention strategies. TRIAL REGISTRATION: Thai Clinical Trials Registry: TCTR20250929005.