Cruise ships do have diagnostic testing capabilities on board...

Cruise ships do have diagnostic testing capabilities on board and much more. I paid to go on a Princess Cruise ship's tour once. I was surprised by the medical facilities. They can treat you on board for just about anything these days, so a helicopter evacuation is very rare. There was a 6-bed ward plus a 2-bed ICU ward and a doctor's consultation room plus a huge supply of medicines, x-ray machine, path lab, nurses and doctors. They can plaster up broken bones and operate on you. Oh and a morgue...

I can't help thinking the spread of any virus would be more likely amongst the low paid crew, than the passengers and management staff. Our tour also included the crew's cabins. Well management do ok, they get nice a nice cabin but we left feeling dismayed about the way the rest of the crew are expected to bunk down. Same size cabins as the majority of passengers, but 6 or 8 staff members packed in, in bunk beds all sharing one tiny en suite. The Captain and management crew were mainly UK/USA/European heritage. The waiters, cleaners, kitchen hands, etc were mainly Asian heritage, especially Philippino and Thai. They typically spend six months at a time on the cruise ship, so the medical facilities were also available to them for GP appointments etc. The crew members we spoke to said all their wages were sent home to support family and they really missed their children. They worked very long hours and sightseeing opportunities were infrequent.

We came away feeling like our luxury cruise experience was at the expense of the very poor Asian working class :-(