[1] Univ London Imperial Coll Sci Technol & Med, Healthcare NHS Trust, Dept Virol, London, England
[2] Alder Hey Childrens NHS Fdn Trust, Dept Paediat Infect Dis & Immunol, Liverpool, Merseyside, England
[3] Great Ormond St Hosp Sick Children, Dept Histopathol, London WC1N 3JH, England
[4] Univ London Imperial Coll Sci Technol & Med, Healthcare NHS Trust, Dept Paediat Infect Dis, London, England