Flat White

The corona clampdown: are we just being silly over sniffles?

19 April 2020

5:19 PM

19 April 2020

5:19 PM

There has been a lot of confusion around COVID-19 statistics and what they means. The fundamental problem is that there is inadequate data as far as the statistics of the disease itself is concerned, how the data are collected and what it all means.

First, you have what is called Infection Fatality Rate, or IFR. This is calculated using a simple formula:

It is important to note that while on the face of it this is a very simple formula, the detail is quite complex.

First, let’s take the total number of fatalities due to the disease. Until the disease runs its course, this is a moving feast. Even if it is known exactly which people died from the disease, what number of infected people do you include? If you only take people who have fully recovered, then the IFR will be too high, as people will usually die from the disease more quickly than fully recover. However, if you include all infected, even those still fighting the disease, then the fatality rate will be too low as some of those still infected will likely succumb. Then there is what actually caused the person to die: did they die from the disease, or with the disease. For example, if I have a cold and die of a heart attack, I died with a cold, not from a cold. Professor Walter Ricciadi, senior adviser to the Italian health minister, says that only about 12 per cent of the fatalities stated to be with coronavirus actually died from coronavirus, the other 88 per cent died from other means. As such, as far as the numerator is concerned, this is likely to be an overestimate of the number of people that actually died from the disease. Another example of this is that of pneumonia deaths in the US. Take a look at the chart. You can see that the number of pneumonia deaths this year has dropped considerably compared with previous years. This is likely due to many of these deaths, where the person also had coronavirus, being put down with coronavirus as the cause of death.

Then we have the denominator. Problematically, this number will be an underestimate of the number of people infected, further exacerbating the calculated IFR; it will be too high both from a too large numerator and too small numerator. So, why is the denominator too small? This is due to testing. The entire community is not tested, only some, and this will disproportionately be those who are more likely to be infected, as they are the important one to diagnose from the point of view of treating them. Then you have a lot of people who are asymptomatic or have very mild symptoms who will not be tested. Additionally, without using an antibody test, if someone has recovered from the disease, they will never show up in the numbers of people infected.

So, how do we get a handle on this? Probably the best way is to consider overall fatalities and compare with previous years around the same time to see whether there is an excess of deaths. In the absence of other significant fatal infections going around, these could reasonably ascribed to the fatal disease going around.

Using the excess deaths situation, let’s have a look at data for Europe. First, we will look at the Z-score graphs. Basically, what you are looking for is deaths above the top line for each of the countries in question. The bright blue lines correspond to the period that coronavirus has been an issue in each country. Looking at the graphs, you will see that there have only been significant excesses in Spain, Italy, the Netherland, Belgium and the UK. In many cases, it can be seen that the severity is not as bad as it was for the flu in 2016/17.

We can look at this in terms of actual maps. Yellow corresponds to no info, and the darker the shade of blue, the higher the rate of excess deaths. The first graph is week 15 this year. Note that only Italy, Spain, England, Belgium and the Netherlands have the darkest blue.

The next graph is for the beginning of 2017, a bad flu season. Notice that there was more dark blue than is currently the case.

So, ask yourself the question, is all the pain we are putting ourselves worth it, or should we, as is my view, relax the restrictions considerably, and allow most of the economy to function? Of course, use sensible social distancing, and perhaps isolate the vulnerable demographics until the disease has worked its way through the community, such as places like Taiwan are doing with great success.

Put it another way, in the early twentieth century, there were a lot of terrible diseases in the community: measles, rubella, TB, polio and so forth. Should they have shut the country down for all those diseases?

Illustration: Tiger Aspect Productions.