1. Centre for Infectious Disease Control; Epidemiology and Surveillance Unit; RIVM PO Box 1, 3720BA Bilthoven The Netherlands
2. Hubert Department of Global Health; Rollins School of Public Health, Emory University; 1518 Clifton Road Atlanta Georgia 30322 USA
3. Expertise Centre for Methodology and Information Services; RIVM; PO Box 1 3720BA Bilthoven The Netherlands
4. Department of Medical Microbiology and infection Control; VUMC Amsterdam van der Boechorststraat 7 1081 BT Amsterdam The Netherlands
5. Centre for Infectious Disease Control; Laboratory for Zoonoses and Environmental Microbiology; RIVM PO Box 1 3720BA Bilthoven The Netherlands
6. Department of Epidemiology Research; Statens Serum Institut; 5 Artillerivej 2300 Copenhagen S Denmark