[1] Publ Hlth England, Emerging Infect & Zoonoses Sect, Natl Infect Serv, London NW9 5EQ, England
[2] Publ Hlth Wales, Toxoplasma Reference Unit, Cardiff, S Glam, Wales
[3] London Deanery, London, England
[4] Publ Hlth England, Stat Modelling & Econ Dept, Natl Infect Serv, London, England