European investigation into recent norovirus outbreaks on cruise ships: update Koopmans, M and Harris, J and Verhoef, L and Depoortere, E and Takkinen, J and Coulombier, D and International outbreak investigation team, Collective, Weekly releases (1997–2007), 11, 2997 (2006), https://doi.org/10.2807/esw.11.27.02997-en