Gillespie Iain A, O'Brien Sarah J, Neal Keith R, Frost Jennifer A, Cowden John M, Syed Qutub
Health Protection Agency Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ, UK.
J Infect. 2005 Apr;50(3):265-7. doi: 10.1016/j.jinf.2004.02.003.