1. Molecular and Cell Biology Team, LGC, Teddington, United Kingdom
2. Virology Laboratory, Clinical Microbiology and Virology, University College London Hospital NHS Foundation Trust, London, United Kingdom
3. Statistics Team, LGC, Teddington, United Kingdom
4. National Institute of Biology, Ljubljana, Slovenia
5. Department of Infection, Division of Infection and Immunity, University College London, London, United Kingdom