Mrs. C.B.M.B. JagerUniversity Medical Center GroningenTh e University of Groningen Department of Medical Microbiology Division of Clinical VirologyDe Brug, Room 2.028. Mailcode EB80 Hanzeplein 19713 GZ Groningen Th e Netherlands Tel: + 31 50 3610223; Fax: + 31 50 3619105