[1] Hokkaido Univ, Fac Med, Dept Publ Hlth, Sapporo, Japan
[2] London Sch Hyg & Trop Med, Dept Infect Dis Epidemiol & Dynam, London, England
[3] London Sch Hyg & Trop Med, Ctr Math Modelling Infect Dis, London, England
[4] Nagasaki Univ, Sch Trop Med & Global Hlth, Nagasaki, Japan
[5] Natl Ctr Global Hlth & Med, Inst Global Hlth Policy Res, Bur Int Hlth Cooperat, Tokyo, Japan
[6] Sapporo Municipal Govt, Hlth & Welf Bur, Publ Hlth Off, Sapporo, Japan
[7] Hokkaido Univ, Kita 15,Nishi 7,Kita Ku, Sapporo 0608638, Japan