To asses the role of virus load in the pathogenesis of hemorrhagic fever with renal syndrome, the serum Dobrava virus RNA load in 46 patients was measured with a novel quantitative real-time reverse-transcriptase polymerase chain reaction assay and compared to the disease severity. The level of viremia, detected in 26 patients, ranged from 10(2)-10(8) copies/mL of serum. The patients with severe disease had, on average, higher viral RNA loads than patients with a milder course of disease (6.15 vs. 4.67 log(10) copies/mL; P = .053). These results suggest that the Dobrava virus load might be associated with the severity of disease.