Affiliation: | Email: ;Centre for Public Health, Liverpool John Moores University, Liverpool L3 2AB;Greater Manchester Health Protection Unit, Manchester M30 ONJ;Communicable Disease Surveillance Centre North West, Chester CH1 4EF;Centre for Public Health, Liverpool John Moores University;Email: ;St Mary''s Hospital, London W2 1NY;St Mary''s Hospital, London W2 1NY |