Multiple exposures during a norovirus outbreak on a river-cruise sailing through Europe, 2006 Verhoef, L and Boxman, IL and Duizer, E and Rutjes, S A and Vennema, H and Friesema, I H and de Roda Husman, A M and Koopmans, M, Eurosurveillance, 13, 18899 (2008), https://doi.org/10.2807/ese.13.24.18899-en