1. Environmental Research Institute; University College Cork; Cork Ireland
2. Department of Infectious Disease Epidemiology; Imperial College London; London UK
3. Institut Pasteur; Biology of Infection Unit; National Reference Centre and WHO collaborating centre for Listeria; Inserm Unit 1117 Paris France
4. Division of Infectious Diseases and Tropical Medicine; Necker-Enfants Malades University Hospital; APHP; Paris France
5. University of Helsinki; Helsinki Finland
6. Warwick Medical School; University of Warwick; Coventry CV4 7AL UK