[1] United Bristol Healthcare Trust, Royal Hosp Sick Children, Bone Marrow Transplant Unit, Bristol BS2 8BJ, Avon, England
[2] United Bristol Healthcare Trust, Royal Hosp Sick Children, Dept Radiol, Bristol BS2 8BJ, Avon, England
[3] Publ Hlth Lab Serv, Dept Virol, Bristol, Avon, England