The passengers on the cruise ship were "confined" to their staterooms/cabins most of the time, but the crew was not confined to theirs or isolated from the passengers (some contact was necessary to deliver meals to them). As Styx pointed out in today's update, all it took to further spread the virus in spite of the restrictions on the passengers was one infected crew member...I came across a news item this morning where authorities in Hong Kong think the virus may be transmitted through a building's pipes. I'd guess this bears watching. It might possibly explain the cruise ship situation....or not.
In another video, the reported number of passengers who have tested positive for the virus on the ship is now over 300.
It is now believed (again) that the virus can be spread by individuals who do not yet have symptoms (which may take three weeks to develop) and the virus may remain active on surfaces for well over a week and the government of China is no longer including people who tested positive but are asymptomatic in the total of infected persons.
Meanwhile, another civilian journalist has disappeared:
Regarding spreading the virus through a building's pipes, it may be spread when an infected person flushes the toilet (especially with the lid up).