Kinetics of human infection with Kyasanur Forest Disease Virus

Kyasanur Forest disease (KFD) was first reported in 1957 and became an emerging tick-borne viral disease of public health importance in India. However, very little is known about the host-virus interaction and pathogenesis of KFD in humans. This study described the presence, duration, and kinetics of KFDV RNA in body fluids in infected human cases.

We enrolled 76 laboratory-confirmed KFD individuals and followed them up in the study. We obtained serial samples of blood, throat swabs in viral transport medium (VTM), urine, stool, and semen during the acute and convalescent phase of KFD illness. In addition, specimens were inactivated, and nucleic acid was extracted and tested for KFDV real-time reverse transcriptase -PCR. Clinical data was also obtained from the subjects.

The study provides evidence of KFD virus RNA in different biological body fluids of humans. The percentage positivity of KFDV RNA in blood was 100% during the first four days of illness. PCR became negative in most cases by 7-8 days; a subset of cases (14%) had prolonged viremia for up to 15 days post-onset of illness. Relatively low copies of KFDV RNA were also detected in throat swabs and urine in the first week of illness. In addition, we detected KFDV RNA in stool samples of cases of those who had diarrhea at an early stage of infection.

The study provides evidence of KFDV RNA in different biological body fluids, which will help understand the pathogenesis, transmission pattern and develop diagnostic algorithms of KFDV in humans. In Kyasanur Forest disease infection, the blood has more RNA copies/ml than other body fluids, and viremia may last up to two weeks post-infection.