JC virus

JC virus infection is usually acquired in childhood or early adolescence with seroconversion rates rising from approximately 90% in young adults to almost 100% in the elderly. Primary infection in healthy subjects is essentially asymptomatic with virus persisting thereafter in the kidneys, CNS (brain) and peripheral white blood cells. Reactivation and shedding of virus can occur in the urine of pregnant women and organ transplant recipients without clinical sequelae. In patients with depressed cell mediated immunity including AIDS and transplantation, reactivation can occasionally result in severe, usually fatal, central nervous system disease (PML).

BK virus

BK virus is usually acquired in early childhood with seroconversion rates rising to nearly 100% by the age of 10-11 years. Primary infection in healthy subjects is essentially asymptomatic with the virus persisting thereafter in the kidneys and peripheral white blood cells. Reactivation of the virus with shedding in the urine occurs frequently in the immunosuppressed and has a low predictive value for BK virus disease. BK viraemia is a better correlate of BK virus nephropathy in renal transplant recipients and is probably also a better predictor of BK disease in haematopoietic stem cell transplant patients.