Comparison of Clinical and Laboratory Characteristics in Patients Between COVID-19 and Respiratory Syncytial Virus Infections

Background: COVID-19 and respiratory syncytial virus (RSV) are 2 distinct yet significant causes of respiratory infections worldwide. Although public attention has primarily focused on COVID-19, RSV remains a serious yet under-recognized threat, especially in adults. Methods: This study retrospectively analyzed the clinical characteristics and laboratory findings of 542 COVID-19 and 332 RSV outpatients treated at the Renji Hospital fever clinic between January 2023 and January 2024. Results: Compared with RSV patients, COVID-19 patients had a higher incidence of diarrhea and older age ( P = 0.016 and <0.001, respectively). COVID-19 patients also exhibited lower counts of white blood cell (6.55×10 9 /L vs. 7.41×10 9 /L, P < 0.01), neutrophil (4.96 ×10 9 /L vs. 5.03 ×10 9 /L, P = 0.033), lymphocyte (0.86 ×10 9 /L vs. 1.46 ×10 9 /L, P < 0.01), eosinophil (0.03 ×10 9 /L vs. 0.10 ×10 9 /L, P < 0.01), and platelet (190.00 ×10 9 /L vs. 216.50 ×10 9 /L, P < 0.01), but showed elevated serum amyloid A levels (33.53 vs. 21.62 µg/mL, P = 0.001). Multivariate logistic regression and receiver operating characteristic analysis demonstrated that lymphocytes and eosinophils were valuable markers for distinguishing RSV from COVID-19, with area under the curve values of 0.779 (95% CI: 0.749-0.810, P < 0.001) and 0.769 (95% CI: 0.737-0.800, P < 0.001), respectively. Conclusions: This study suggests that differences in lymphocyte and eosinophil counts serve as noteworthy indicators for distinguishing between COVID-19 and RSV infections in the early stages, providing valuable supplementary information.