HHV-6 encephalitis refers to inflammation of the brain due to an infection with human herpesvirus 6. People who have undergone allogeneic hematopoietic cell transplantation are at an increased risk for developing HHV-6 encephalitis, particularly when umbilical cord blood stem cells are used. People with immune system disorders may also be at an increased risk for developing this infection. Signs and symptoms vary, but often include confusion, anterograde amnesia (difficulty learning new information following the onset of amnesia), short-term memory loss, and seizures.Diagnosis often involves lumbar puncture, virus testing, and MRI. EEG 's may also be recommendedwhen seizures are suspected. HHV-6 encephalitis is treated with an antiviral agent with activity against HHV-6. Long term outlook (chance of full recovery) can vary considerably depending individual patient factors. The disease is HHV-6 encephalitis (Monarch Disease Ontology term MONDO_0027029).