The Diamond Princess, a floating Chinese Virus palace, provides suggestive data

What's frightening about the Chinese Virus is the overwhelming amount of inconclusive information.  We're inundated with media speculation and hyperventilation, Chinese disinformation, and data that change daily thanks to the treatment and quarantine initiatives governments are trying around the world.

The fact that the disease has different rates of contagion and mortality in different parts of the world makes things more confusing.  We can understand why it exploded in China, a place of censored information, pollution, smoking, and primitive socialized medicine.  But why was it so virulent in Italy?

Surely, Italy's socialized medicine is better than China's.  Or is the problem Italy's recent Silk Road Project agreement with China, which resulted in more than three hundred thousand Chinese workers entering Italy, mostly in the north, along with constant traffic between the two countries?  Although the mainstream media celebrated the deal as a slap at Trump, in hindsight, it may have had disastrous consequences for Italy.

Fortunately, there is one almost "pure" location for coronavirus data, and that is Princess Cruise's Diamond Princess cruise ship.  This was the ship moored along Japan's coast while the government tried to determine the best way to deal with a floating virus bomb.  Writing at Watts Up With That, Willis Eschenbach looked at the Princess Cruise's numbers and discovered some encouraging information:

We had a perfect petri-dish coronavirus disease (COVID-19) experiment with the cruise ship "Diamond Princess". That's the cruise ship that ended up in quarantine for a number of weeks after a number of people tested positive for the coronavirus. I got to wondering what the outcome of the experiment was.

So I dug around and found an analysis of the situation, with the catchy title of Estimating the infection and case fatality ratio for COVID-19 using age-adjusted data from the outbreak on the Diamond Princess cruise ship (PDF), so I could see what the outcomes were.

As you might imagine, before they knew it was a problem, the epidemic raged on the ship, with infected crew members cooking and cleaning for the guests, people all eating together, close living quarters, lots of social interaction, and a generally older population. Seems like a perfect situation for an overwhelming majority of the passengers to become infected.

And despite that, some 83% (82.7% – 83.9%) of the passengers never got the disease at all … why?

What an excellent question.  Why did 83% of the ship's passengers walk away unscathed?

It's an especially good question because the majority of passengers were in the 60–79 age group, weighted slightly more heavily toward the 70–79 cohort.  In other words, by the time the ship docked, it should have been a floating morgue, but somehow it wasn't.

When Eschenbach looked at those on the ship who did not get sick, he discovered something equally intriguing:

[T]here's not a whole lot of difference between young and old passengers in terms of how many didn't get coronavirus. For example, sixty to sixty-nine-year-old passengers stayed healthier than teenagers. And three-quarters of the oldest group, those over eighty, didn't get the virus.

And here's where it gets really interesting because it has to do with the denominator — that is, the number of people who get sick.  Because the Diamond Princess was monitored, we know precisely how many people got sick, and we know they would never have been noticed were they not on the ship:

Next, slightly less than half the passengers (48.6% ± 2.0%) who got the disease showed NO symptoms. If this disease is so dangerous, how come half the people who got it showed no symptoms at all?

What's fascinating is that the group most likely to show symptoms was people aged 20–49.  Children under 9 were almost entirely without symptoms.  And here's the big surprise: people aged 70-79 tied with young people 10–19 when it came to being ill without symptoms.

Thankfully, only seven people died, all of whom were over 70.  From this data, Eschenbach had some provocative and comforting conclusions:

It is particularly valuable to know that about half the cases are asymptomatic. It lets us adjust a mortality rate calculated from observations, since half of the cases are symptom-free and likely unobserved. It also gives a better idea of how many cases there are in a given population.

To close out, I took a look at the current state of play of total coronavirus deaths in a few selected countries. Figure 4 shows that result.

Figure 4. Deaths from coronavirus in four countries. Note that the scale is logarithmic, so an exponential growth rate plots as a straight line. Blue scale on right shows the deaths as a percentage of the total population.

At this point at least, it doesn't appear that we are following the Italian trajectory. However … it's still early days.

By now, one has to ask if there are genetic vulnerabilities and defenses affecting whole nations.  Or do Americans just wash their hands more often?  All these answers remain to be seen, but perhaps coronavirus won't be that bad at the end of the day.

UPDATE: This article originally said the Diamond Princess was held off of California. It was the Grand Princess that was alongside California. I've since corrected the error.

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