Preliminary tests identified the source of the outbreak as the highly contagious norovirus, which had struck several guests just before they boarded the cruise Nov. 3 in Rome, Carnival officials said.
the guests boarded the cruise in halifax
( z1 board :ARG0 ( z2 guest ) :ARG1 ( z3 cruise ) :location ( z4 city :name ( z5 name :op "Halifax" ) ) )