BACKGROUND: Viremia has been detected in a significant proportion of patients with acute respiratory viral infection, yet its clinical value remains underappreciated. OBJECTIVES: This study synthesized available evidence to comprehensively assess the prevalence of viremia and its impact on clinical outcomes. METHODS: Data sources: Data were retrieved from Medline (via Ovid), Embase, and the WHO COVID-19 database. STUDY ELIGIBILITY CRITERIA: This review included original clinical studies analysing the prevalence of viremia in patients with acute respiratory viral infection or its association with clinical outcomes, while excluding non-original research, insufficiently detailed studies, inconsistent pathogen observations, or those with inadequate sample sizes. PARTICIPANTS: Patients with acute respiratory viral infection. ASSESSMENT OF RISK OF BIAS: Newcastle-Ottawa scale and an adapted version were used. EXPOSURE: Respiratory viral infection-related viremia. METHODS OF DATA SYNTHESIS: Data synthesis utilized random-effects models to pool prevalence and hazard ratio (HR), OR, and adjusted HR/OR for clinical outcomes. RESULTS: In the comprehensive analysis of viremia prevalence, data were pooled from 101 studies, which included a total of 16,388 non-overlapping patients. Viremia was present in 34% (95% CI, 28-41%) of patients with acute respiratory viral infection. A total of 45 studies provided information on the clinical outcomes of 2002 patients with viremia and 3907 patients without viremia. Viremia was associated with increased risks of mortality (OR, 6.83
95% CI, 4.92-9.48
adjusted HR, 2.91
95% CI, 1.87-4.53
adjusted OR, 3.68
95% CI, 2.37-5.71), intensive care unit admission (OR, 4.74
95% CI, 2.66-8.46
adjusted OR, 4.89
95% CI, 1.61-14.91), mechanical ventilation (OR, 4.12
95% CI, 2.25-7.52), and hepatic complications (OR, 3.10
95% CI, 1.30-7.40). CONCLUSIONS: Viremia is prevalent in patients with respiratory viral infection and is associated with elevated risks of adverse clinical outcomes.