When looking at official figures, it seems that there were very few cases of coronavirus in China. However, analysis of blood samples taken during the pandemic reveals a quite different story.
The official figures
When looking at the coronavirus cases data around the world, for example on Bloomberg, we see something like this:
When looking at it, the first reaction we could have is “Woah! China is so efficient! It’s even way better than Japan, with 20 times less cases per person.” However, I will show that we should have some doubts about these outstanding results.
The number of cases per million people can be biased by two factors.
The availability of tests: The more people we test, the more cases we find.
The honesty of government: We rely on governments to report the number of cases, so a dishonest government can simply report incorrect data. Note here that if the government is authoritarian (like China) it is easier for them to report fake data since people internally won’t be allowed to tell the world that the government is lying.
Using blood samples to tell the truth
It might seem here that we can’t know anything for sure and we just have to trust governments. However, there is actually a way to get closer to the truth. We can analyze blood samples which have been made during the pandemic for other reasons than COVID testing, and see if we find antibodies against the coronavirus. Using this data, we can retroactively estimate how many coronavirus cases there were during the first wave of the pandemic. In the edition of September 26th, 2020, The Economist presented such a study. The method they used is very transparent and all data and source code are available.
Let’s look at their results, here is the graph which shows the number of estimated cases with this method:
Now let’s compare it to official figures after the first wave in Europe and the US was over. Here are the numbers that were reported on May 28th, 2020:
Don’t you find that there's a striking difference? In the official numbers, the United States appears the worst country on Earth with 1.7 million cases, far higher than any other. However, in the estimation based on blood samples, there were actually more cases in China than in the US during the first wave. This contradicts the official figures, according to which there were 20 times more cases in the US than in China. In the estimation, we can see that there are more than 1 million cases per day in China at the peak of the wave in February, while the official Chinese figure claims a total of only 83,000 cases. How can there be less than 100,000 people infected in total when there were already a million people infected every day during February?
I don’t want to necessarily imply that the Chinese government deliberately lied about the number of cases. In the beginning of the pandemic, testing was not widely available, and it is completely possible that they simply didn’t test enough people. However, the point I want to make is that the official figures of the total number of confirmed cases are very misleading when comparing countries.
A massive underestimation
Digging further, scientists were able to calculate how much each country underestimated the number of cases. They find for instance that the real number of cases in the United States is 7 times the number of reported cases! This looks enormous but it can be understood because not everyone who gets the virus gets tested. But in fact, an underestimation by “only” a factor of 7 is among the best in the world! Compare it to England (14x), Spain (10x), Sweden (17x), Russia (27x). Less advanced countries get even more massive underestimation factors, for example India (271x) and Nigeria (1,595x). So, to summarize, one of the reasons why the total number of cases in the US in the first wave is so high is because it is one of the most honest and accurate figures.
I am not claiming that the United States did the best pandemic management in the world, far from it. Some countries were clearly much more successful, like Japan, South Korea and Taiwan. One might argue that it’s only a matter of culture, population age or genetics, but even some Western countries like Germany did a much better job than the US. However, I think we should be very skeptical when looking at data that shows China as the best pandemic management in the world.
As a final point, let’s look at the world globally. This blood data suggests that the number of people who got the virus in the world is between 500 million and 730 million (in September), far above the official number of about 70 million cases (even now in December). So it seems that at the world level, we are underestimating the number of cases by a factor around 10.
And you, what do you think? Feel free to give your insights or other sources.
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