[1] HPA Microbiol Serv Div, London NW9 5HT, England
[2] Microbiol Serv Bristol Virol, Dept Microbiol, Bristol BS2 8EL, Avon, England
[3] Royal Victoria Infirm, Leazes Wing, Newcastle Upon Tyne NE1 4LP, Tyne & Wear, England
[4] Minist Hlth, Publ Hlth Serv, IL-91010 Jerusalem, Israel
[5] Southampton Gen Hosp, Publ Hlth Lab Southampton, Hlth Protect Agcy, Southampton SO16 6YD, Hants, England
[6] Manchester Royal Infirm, Manchester Med Microbiol Partnership, Manchester M13 9WL, Lancs, England