Number of China coronavirus virus cases rises to 1,975. Why that number is statistically impossible

Author: Adam Button | Category: News

Here is why I think that's wrong


China has now confirmed 56 deaths and 1,975.

For reference to total number of global SARS cases were 8089 and it cut around 1 percentage point from Chinese GDP. That pandemic also moved much more slowly. To me, this will undoubtedly be worse.

In any case, this is about the official number. It's now progressed like this:

  • Jan 17: 41
  • Jan 19: 62
  • Jan 20: 201
  • Jan 21: 291
  • Jan 22: 440
  • Jan 24: 830
  • Jan 25: 1,287
  • Jan 26: 1,975
Those numbers are terrifying but I'm about to scare you much more. Here's why the latest number is statistically impossible, and almost certainly far too low.

Canada became the latest country to confirm a case of coronavirus. That brings the total number of people infected abroad to at least 32 by my count. At least 30 of them have a direct connection to Wuhan city and yet that province has only reported 761 cases.

That means there is one foreign case directly tied to Wuhan for every 25 cases in the city. Put differently, that means that in the short window of incubation -- two weeks at most but probably half that -- one in every 25 people in the city would have had to travel abroad -- or about 433,639 people.

To put that into perspective, Sweden is the most well-traveled country in the world and has almost the same population as Wuhan (11 million). The average number of international trips each day is just over 30,000. If you were adjust for people who took multiple trips per year that would conservatively fall to 20,000. Nevermind that Sweden is one of the richest countries in the world and travel to the rest of Europe is extremely cheap and easy. But citizens of Wuhan would have had to travel abroad at more than twice the rate of Swedes for the 761 number from Wuhan to be even remotely possible.

This is the exact methodology that the MRC Centre for Global Infectious Disease Analysis used on January 17, when China had reported just 41 cases they estimated 1700 cases.

This epidemic is far worse than the reported numbers, but China's efforts to seal off +50 million people and shut down a dozen cities already told you that.

Still not scared? A big debate in the virus community right now is the basic reproduction number of this virus. That's how many people each person passes it to, on average. If it's 10 that means it spreads very quickly, if it's less than 1 it inevitably dies out. A new paper from China pegs it at 3.3-5.5 and at this point that basically means it's unstoppable baring some intense quarantines and a bit of luck. Another paper initially had it at 3.8 but has scaled that back to 2.5 and another in the UK (cited below) has it at "2.6 or higher."

You can still stop an epidemic at that point but you need to contain 60% of cases.

Yet even at that level, here's what Neil Ferguson, an infectious disease modeller/epidemiologist and Director of J-IDEA and the MRC Centre for Global Infectious Disease Analysis says the outlook is bleak:
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Still not scared? Another paper estimates that the mortality rate of coronavirus is 15%.

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