Ongoing multi-strain food-borne hepatitis A outbreak with frozen berries as suspected vehicle: four Nordic countries affected, October 2012 to April 2013. - Gillesberg Lassen S; Soborg B; Midgley SE; Steens A; Vold L; Stene-Johansen K; Rimhanen-Finne R; Kontio M; Löfdahl M; Sundqvist L; Edelstein M; Jensen T; et al. (Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin, 2013)