From the aDepartment of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College, London
bDepartment of Epidemiology and Population Health, London School Of Hygiene and Tropical Medicine, London, UK
cUnité de recherche en santé des populations, Hôpital du Saint-Sacrement, Centre Hospitalier Affilié Universitaire de Québec
dDépartement de médecine sociale et préventive, Faculté de médecine, Université Laval, Quebec, Canada.
Received 28 September, 2005
Revised 12 November, 2005
Accepted 6 December, 2005
Correspondence to Rebecca Baggaley, (present address) Modelling Unit, Department of Statistics, Modelling and Bioinformatics, Centre for Infections, Health Protection Agency, 61 Colindale Avenue London, NW95EQ UK. E-mail: [email protected]