[1] UCL Royal Free & Univ Coll Med Sch, Dept Virol, Windeyer Inst, London W1T 4JF, England
[2] Birmingham Heartlands Hosp, Publ Hlth Lab, Dept Virol, Birmingham B9 5SS, W Midlands, England
[3] Natl Blood Serv, N London Ctr, London NW9 5BG, England
[4] UCL Royal Free & Univ Coll Med Sch, Dept Sexually Transmitted Dis, Mortimer Market Ctr, London WC1E 6AU, England