Roseoloviruses in transplant recipients: clinical consequences and prospects for treatment and prevention trials

•HHV-6A and HHV-6B are now classified as distinct species with important differences.•Chromosomally integrated HHV-6 may be a source of viral reactivation and disease.•HHV-6B is associated with a spectrum of CNS symptoms.•Limited HHV-6 preemptive and prophylactic studies have not shown improved outcomes.•Large trials will help inform the significance of Roseoloviruses after transplant.

Roseoloviruses frequently reactivate in transplant recipients. We review the impact of Roseoloviruses in transplant recipients and highlight research priorities. Human herpesvirus 6A (HHV-6A) and HHV-6B were recently classified as distinct species with important differences. Both viruses can result in inherited chromosomally integrated HHV-6, which may cause complications after transplant. HHV-6B is the primary species associated with disease and appears to have pleiotropic effects on the central nervous system. Small preemptive and prophylactic studies have not shown a statistically significant impact on HHV-6 disease. Although Roseoloviruses are associated with diverse complications in transplant patients, studies providing strong evidence for a causal role are lacking. Trials focusing on prevention and treatment will be important to inform the significance of Roseolovirus reactivation.