Abstract
Objectives: Objectives: SARS-CoV-2 virus dynamics in the human body and its correlation with disease severity and biomarkers have not been elucidated. This study aims to evaluate the viral load in the blood sample of COVID-19 patients and viral load association with disease severity and progression.<br>Methods: Blood samples from COVID-19 positive inpatients were collected sequentially, at admission, and during hospitalization. Depending on the clinical presentation, the patients were classified into mild, moderate, and severe categories. The blood samples were subjected to SARS-CoV-2 Real-time polymerase chain reaction (RT-PCR); positive samples were then tested for viral load using digital drop RT-PCR. Patients were followed up until they were discharged.<br>Results: Of 83 enrolled patients, 15 (18.1%) were mild, 45 (54%) were moderate, and 23 (27.7%) had severe symptoms. The blood PCR in 21 patients was positive (rate was 25.3); one was mild, four moderate, and 16 severe on the day of admission. The mean cycle threshold (CT) of RNAemia in these 21 patients was 24.7+3.1. The viral load was significantly higher in patients with severe symptoms than others. Serum ferritin, D-dimer, and plasma fibrinogen were found raised along with lymphopenia in all patients. Viremia was found persistently detectable (or even rising) in patients in the severe category and associated with a fatal outcome.<br>Conclusion: A prolonged elevation of D-dimer, serum ferritin, and plasma fibrinogen together with lymphopenia lead to a greater risk of mortality and morbidity. Quantitative estimation of virus in blood has a clinical significance which may help in prognostication and management of patients of COVID-19. J Microbiol Infect Dis 2021; 11(3):116-123.

Key words: SARS-CoV-2, Viremia, Digital drop PCR, Serum ferritin, D-Dimer, Lymphopenia, Plasma fibrinogen, Procalcitonin