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.
Norovirus spreads more easily on cruise ships.
( z1 spread :ARG1 ( z2 virus :name ( z3 name :op "Norovirus" ) ) :location ( z4 ship :mod ( z5 cruise ) ) :ARG1-of ( z6 have-degree :ARG2 ( z7 easy :ARG1 z1 ) :ARG3 ( z8 more ) ) )