Behind the Reproduction Number

  • Fiction

So far I have derived as much insight as possible from two series of simple numbers, thought Mr. Node, the weekly numbers of COVID infections and the weekly numbers of COVID deaths. I copied them from the databases that were set up immediately as soon as it became clear how badly the virus spread and damaged people. It started in Wuhan in the last week of 2019, as an unknown, Sars-like virus with a few affected. In the first week of February, public life was curbed across China and two emergency hospitals with a capacity of around 2,000 ICU places were set up in Wuhan. In other words, by week 5 it was clear that something rather serious was going on.


Reproduction numbers

Weekly reproduction numbers are important in understanding pandemics, especially in the early weeks. They then indicate how the virus spreads without countermeasures. Assuming that the way the virus works is independent of the country in which it infects the people, Node expected to find a constant value for the initial reproduction number in the different jurisdictions. But as he had already shown elsewhere, the observed numbers differ per jurisdiction. These differences are shown in a table on the left. How can the differences be explained? The numbers are in descending order. The dates of entering the jurisiction is in a similar order: China was the first, and Brazil the last country to see COVID-19 cross its borders. An explanation for the declining initial reproduction numbers may be that the later the introduction happens, the better the population becomes informed about the dangers and consequently attempts to behave more cautiously. The way in which government leaders position themselves will be important to such behavioral choices. The differences between the USA, France and the UK on the one hand and the Netherlands (also 1 week later) on the other could be partly explained by the initially trivializing (Trump, Johnson) or preoccupied (Macron, pension-system reform perils) attitudes of the local government leaders of the first three mentioned jurisdictions, compared with Rutte’s positioning in the Netherlands.

Mr. Node consequently assumes that R0 (the reproduction number in the first week of the pandemic) is approximately equal to 4, and that it is possible to bend the number downwards by the use of rules of conduct. Lock-downs in a one-and-a-half meter society without large group meetings and without singing/shouting/dancing together but with regular hand disinfection (further: the measures) have proven to work.

But these measures have serious social and economic consequences. Entire economic sectors must (temporarily?) close or adapt: ​​(major) sports, religious, cultural, academic and social events and festivals had to be canceled. And in those jurisdictions where the measures are not observed or are taken too late or half-heartedly, the pandemic continues or re-emerges.

What the first analysis of the numbers shows is that the measures work, but also that they have side effects that can lead entire tribes to neglect them or at least judge them differently. That means, Node thought, that in order to understand how the pandemic will develop, I need to get a picture of how group behaviors around the measures will develop in varying frameworks of solidarity, justice, economic growth/contraction and evidence-based solution options.

To this end, Node considers, I can use toy-world simulations very well.