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.
Guests boarded the cruise on Nov. 4 in Rome. 
( z1 board :ARG0 ( z2 guest ) :ARG1 ( z3 cruise ) :time ( z4 date-entity :day 4 :month 11 ) :location ( z5 city :name ( z6 name :op "Rome" ) ) )