[1] Karolinska Inst, Microbiol & Tumour Biol Ctr, Lab Tumour Virus Epidemiol, S-17177 Stockholm, Sweden
[2] Ist Nazl Tumori, Ctr Riferimento Oncol, Microbiol Immunol & Virol Dept, I-33081 Aviano, Italy
[3] Natl Publ Hlth Inst, Helsinki, Finland
[4] Social Insurance Inst, Helsinki, Finland
[5] Univ Liverpool, Dept Med Microbiol & Genitourinary Med, Mol Virol Grp, Liverpool L69 3BX, Merseyside, England
[6] Canc Registry Finland, Helsinki, Finland