1 Centre for Infectious Disease Control (Cib), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
2 Department of Viroscience, Erasmus MC, Rotterdam, The Netherlands.
3 Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine (TiHo), Hanover, Germany.
4 Centre for Infectious Disease Control (Cib), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands. [email protected].