[1] Natl Inst Publ Hlth & Environm, Ctr Infect Dis Control, Bilthoven, Netherlands
[2] Univ Amsterdam, Med Ctr, Inst Infect & Immun, Amsterdam, Netherlands
[3] Publ Hlth Serv Amsterdam, Dept Infect Dis, Amsterdam, Netherlands
[4] Natl Inst Publ Hlth & Environm, Ctr Infect Dis Control, Postbox 1, NL-3720 BA Bilthoven, Netherlands