[1] Univ Calgary, Liver Unit, Dept Med, Div Gastroenterol & Hepatol, Calgary, AB T2N 4Z6, Canada
[2] BC Ctr Dis Control, Vancouver, BC, Canada
[3] Univ Montreal, Montreal, PQ, Canada
[4] Univ Manitoba, Winnipeg, MB, Canada
[5] Univ Western Ontario, London, ON, Canada
[6] Dalhousie Univ, Halifax, NS, Canada
[7] Univ British Columbia, Vancouver, BC V5Z 1M9, Canada
[8] Ctr Dis Anal, Louisville, CO USA
[9] Univ Toronto, Toronto, ON, Canada