Likewise stunned when I read that today. If the initial infection was from one person (or a couple) that is an incredible infection rate, exacerbated by the close conditions onboard.

It must be very worrying for owners and crew to be forcibly quarantined en masses, especially the medically vulnerable.

The analysis of the spread onboard must be fascinating. How many hops between infected people? What's the R0? How many carriers and the distribution of their symptom profiles. I'm sure there the experts realise that these choose shops are very valuable sources of information to help shape the fight against the virus.