I have never been on a cruise ship; just the thought of masses of people in close quarters on open water makes me want to barf. Large norovirus outbreaks are associated with settings where people live in close quarters and can easily infect each other, such as cruise ships, dormitories, and hospitals. Contaminated food, water, an infected person are all potential sources of norovirus. Viral contamination of environmental surfaces (fomites) may persist during and after outbreaks and contribute to further illnesses. The source of the Sun princess cruise ship outbreak is currently unknown. 

A norovirus outbreak has struck at least 91 passengers on a Sun Princess cruise ship.
The affected people were treated for gastro after the ship docked in Brisbane on Thursday morning.
A Queensland Health spokesman told Daily Mail Australia: ‘Metro North Public Health Unit is aware of at least 91 cases of gastro on board a cruise ship that berthed in Brisbane this morning.
‘We have been advised that on-board testing has found norovirus to be the cause of the illness.’
It comes after 140 passengers came down with gastro in February after a Sun Princess cruise returned from a 14-day trip around New Zealand.
A fortnight before that, there was another outbreak on the vessel during a previous cruise.