[1] Free Univ Brussels, Acad Ziekenhuis, Dept Microbiol, Belgian Ref Lab Pertussis, B-1090 Brussels, Belgium
[2] Free Univ Brussels, Acad Ziekenhuis, Dept Pediat, B-1090 Brussels, Belgium
[3] Swedsih Inst Infect Dis Control, Solna, Sweden
[4] Natl Inst Publ Hlth & Environm, Res Lab Infect Dis, Bilthoven, Netherlands