Department of Viroscience, Erasmus Medical Center, Rotterdam, 3015GE, the Netherlands. Clinical Virology and Diagnostics, 1817HL, Alkmaar, the Netherlands. Micron, Ely, CB7 4AF, United Kingdom. Roche Products Ltd, Welwyn Garden City, AL7 1TW, United Kingdom. Department of Viroscience, Erasmus Medical Center, Rotterdam, 3015GE, the Netherlands; Department of Pediatrics, Subdivision Infectious Diseases and Immunology, Erasmus Medical Center - Sophia, Rotterdam, the Netherlands. Electronic address: p.fraaij@erasmusmc.nl.