Quantitative analysis of Epstein–Barr virus in upper respiratory tract samples of hospitalized patients with COVID-19

Aim This study investigated the status of Epstein–Barr Virus (EBV) in the upper respiratory tract (URT) samples of patients with coronavirus disease 2019 (COVID-19), with a focus on EBV viral load and lytic gene activity.Methods This retrospective cross-sectional study included 87 hospitalized COVID-19 patients, categorized into favorable (n = 40) and unfavorable (n = 47) outcome groups. URT samples were analyzed using real-time PCR for absolute quantification of EBV DNA based on BALF5 copy number, and EBV lytic activity was assessed via BZLF1 mRNA relative expression.Results EBV DNA was detected in 76 patients (87.4%), and all patients with unfavorable outcomes were EBV-positive. EBV viral load and BZLF1 expression were significantly higher in the unfavorable outcome group compared to the favorable group. EBV viral load was weakly correlated with patient age (p = 0.018), whereas BZLF1 expression showed a moderate positive correlation with longer hospitalization (p = 0.001). EBV viral load was also positively correlated with inflammatory markers, including C-reactive protein, white blood cell count, creatinine, and D-dimer. Moreover, EBV positivity was significantly associated with in-hospital mortality and ICU admission.Conclusion EBV reactivation in the URT may be associated with worse clinical outcomes in hospitalized COVID-19 patients.