Up to 80% of Covid-19 infections are asymptomatic

Sure, it would be great to do a followup, though anybody who left the ship could have contacted other corona people off-boat by now.

In the SF Bay area, the Santa Clara dashboard only shows 5% of those tested being positive (whatever that means, since test results are questionable), but because of the close affinity with China, I'd bet on 80% having been exposed, not 5%.

The lack of follow up is indeed rather frustrating. On the plus side, the article reports that they kept the people in quarantine 8-12 days after the testing round. From other sources on the Web, "on average symptoms appear after 5 days and most people with symptoms had them by day 12". While the study has probably accounted for most of the symptomatic cases, a 30 day follow up would be of great value, including to validate the incubation period estimations.

https://www.webmd.com/lung/coronavirus-incubation-period

No opinions needed, there are too many opinions already floating around. Fact is that the ratio is 1/10, according to all antibody tests worldwide. This also matches the IFR/CRF discrepancy of 0.3%/3.4%.

So 90% is more likely.

And to the opinions: The extremely high dark figure could explain the high reproduction rate of r3.5. People who think they've only got a cold happily will infect others.