[1] Univ Oxford, Canc Epidemiol Unit, Oxford OX3 7LF, England
[2] German Canc Res Ctr, Infect & Canc Program F020, D-69120 Heidelberg, Germany
[3] Lund Univ, Malmo Univ Hosp, Dept Med Microbiol, SE-20502 Malmo, Sweden
[4] Albert Einstein Coll Med, Dept Epidemiol & Populat Hlth, Bronx, NY 10467 USA
[5] Univ York, Dept Hlth Sci, Epidemiol & Genet Unit, York YO10 5DD, N Yorkshire, England