A COVID-19 Interim Report (4): R0-Differences per Week

  • Models

In interim report (3) I formulated an aphorism and tried to test it. It seemed to work in 8 of the 9 jurisdictions I reviewed before. But not for South Korea. More about that here. First a quote:

Aphorism I – Until an effective policy is established in a jurisdiction, the first COVID-19 spread will be exponential, which will only change under the influence of such a policy.

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wk 8-10 (2): 10 march– South-Korea. South Korea is a different story. There have been hardly any government-enacted lock-downs, but there have been recommendations and a significant and widely shared concern for the spread of the pandemic among the population. The focus is mainly on supportive measures (testing, distancing, masks, temperature measurements, quarantine of who has symptoms, contact analyzes). In the three days following February 18, however, the numbers of registered infections rose exponentially in and around Daegu. The source was traced back to a religious gathering of the Shincheonji movement. The COVID-19 explosion involved made a big impression. But it appears that the adoption of the measures came from within the people themselves, not by any rule of law. As far as I can tell, the government is assisting with testing and contact tracking and with making quarantine hotels available. If the Daegu outbreak has been a tipping point, it is to be expected that the curve will rise exponentially with it and will deviate again a month later. No regulation in sight. So it is much more likely that that outbreak occurred in an environment that was already living under the acceptance of the measures based on what had become known during the Wuhan outbreak in China. So what happened in South Korea doesn’t match my aphorism I.

South-Korea as an anomaly for aphorism I

What we see is that the population has still fresh in their minds the dramatic SARS epidemic and, on the basis of previous reports about Wuhan, that people armed themselves against becoming infected by the CVOVID-19 virus, which is regarded as related to SARS. As far as I can tell South-Korea has not needed a top-imposed, mandatory lock-down to get and keep COVID-19 under control.

For the latter, we look at how COVID-19 developed in South Korea in the first 43 weeks. See fig. 1. The weeks are given in the horizontal axis, from 0 to 44 (the last is empty). The horizontal axis shows new numbers of deaths per week (the black curve) and a fraction of the numbers of new infections per week (the red curve). The fraction is chosen such that the maximum of the red curve is equal to that of the red one. That fraction number comes to 91.16. How that can be read will follow later. What I also see is that the relatively large movements in the black curve follow those kinds of movements in the red curve, with a time-lag of about four weeks. That gives me an indication of the duration of a disease course that ends in death. But also about that later.

Fig. 1 – 43 weeks of COVID-19 in South-Korea

The relatively large movements in the red curve are around week 9 and week 34. This ties in with the following observation I take from a newspaper: “While the first peak focused on the country’s third largest city, Daegu , and a mega-church called the Shincheonji Church of Jesus, the second peak this time focuses on the capital and another religious group – the Sarang Jeil Church. ”

This ties in seamlessly with the idea that has now taken hold, partly due to these kinds of observations, that the pandemic can occur in two gears. One way is the slow way, which jumps from person to person and seems to be able to be tamed through social distancing. The other, fast way, usually takes place in poorly ventilated environments where people congregate and talk or sing loudly. Opportunities that ensure COVID-19 to spread in this way are called super-spreaders. Its occurrence must be constrained by limiting group sizes.

Meanwhile it is clear that I have to find a different formulation for aphorism I.