Norovirus strains belonging to the GII.4 genotype dominate as a cause of nosocomial outbreaks of viral gastroenteritis in Sweden 1997--2005. Arrival of new variants is associated with large nation-wide epidemics. - Johansen K; Mannerqvist K; Allard A; Andersson Y; Burman LG; Dillner L; Hedlund KO; Jönsson K; Kumlin U; Leitner T; Lysén M; Thorhagen M; et al. (Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology, 2008)