A coronavirus conundrum, on the percentage of asymptomatic cases

New reports suggest that the coronavirus has been spreading in Washington state for at least six weeks, infecting hundreds or maybe more.  At the same time, other reports suggest a high “R0 value,” sometimes 3 or more, reflecting that the coronavirus is highly contagious and it spreads very quickly.

It is then possible to have hundreds of cases in Washington state if most cases are asymptomatic, or with only slight symptoms.  Yet when we look at the experiences of the coronavirus cruise ships, it seems a reasonable number of cases have symptoms of distress.  For instance, on the Diamond Princess six people died and only about half are listed as having the virus but asymptomatic (see the previous link on the rhs).  So many others seem to have reported being sick or requiring treatment.

So what gives?  I see a few options, none of them obviously convincing:

1. People on the cruise ship were hit especially hard.

2. Significantly different strains of the virus are circulating (all of the sequence that has been done seems to run counter to this).

3. Washington state local public health infrastructure has in fact been overwhelmed as of late, we just thought it was all a very bad flu season.

4. Many of the people on the cruise ship who showed symptoms “thought they were supposed to” but were not actually so sick.

5. Most of the detected cases on the cruise ship in fact were asymptomatic, but the media has been misreporting the extent of actual illness among the passengers.

Any other suggestions?  It is quite likely the cruise ship people are older than usual, but will that make up for the entire difference?  People, what do you think is going on here?

Please restrict your comments to attempting to resolve this particular issue, as you can put your more general coronavirus observations on other posts.