[1] Reg Publ Hlth Lab Kennemerland, Dept Epidemiol & Infect Prevent, Boerhaavelaan 26, NL-2035 RC Haarlem, Netherlands
[2] Municipal Hlth Serv GGD Hollands Noorden, Dept Infect Dis, Grotewallerweg 1, NL-1741 NM Schagen, Netherlands
[3] Gemini Ziekenhuis, Dept Intens Care, Huisduinerweg 3, NL-1782 GZ Den Helder, Netherlands
[4] Natl Inst Publ Hlth & Environm, Dept Epidemiol & Surveillance, Antonie van Leeuwenhoeklaan 9, NL-3721 MA Bilthoven, Netherlands