[1] Univ Birmingham, PHLS Antiviral Susceptibil Reference Unit, Div Immun & Infect, Birmingham B15 2TT, W Midlands, England
[2] Pinderfields Hosp, Dept Genitourinary Med, Wakefield, England
[3] Leeds Gen Infirm, Leeds, W Yorkshire, England
[4] Univ Nottingham, Dept Virol, Nottingham NG7 2RD, England