Department of Microbiology and Immunology, Katholieke Universiteit Leuven, Leuven, Belgium. philippe.lemey@uz.kuleuven.be|Department of Microbiology and Immunology, Katholieke Universiteit Leuven, Leuven, Belgium. philippe.lemey@uz.kuleuven.be|Department of Microbiology and Immunology, Katholieke Universiteit Leuven, Leuven, Belgium. philippe.lemey@uz.kuleuven.be|Department of Microbiology and Immunology, Katholieke Universiteit Leuven, Leuven, Belgium. philippe.lemey@uz.kuleuven.be