1. Municipal Health Service Midden-Nederland, Department of infectious diseases, Zeist, the Netherlands
2. Bartiméus Doorn, Centre for residential care for multiply disabled visually impaired people, Doorn, the Netherlands
3. Hospital Diakonessenhuis Utrecht, Utrecht, the Netherlands
4. Laboratory for Infectious Diseases and Perinatal Screening (LIS), National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
5. Department of Medical Microbiology and Infectious Diseases, Erasmus MC, University Medical Centre, Rotterdam, the Netherlands