Dealing With Uncertainties

There are now 2000 confirmed cases of the Wuhan coronavirus, so we are a little ahead of schedule. This means that the outbreak is in its exponential phase. At this rate, we can expect 4000 cases by mid Tuesday.

The mortality rate for this disease is said to be 3%. However, that number is in conflict with our calculations. The death toll is 3% of the current number of infected people. But to say that the mortality rate is 3% based on this is to understate the true number, which should be calculated based on the number of infected people 2 to 3 days back in time. Mortality is after all a trailing number. It takes about 2 to 3 days for a virus like this to go from identification to its peak severity. Mortality rates should therefore be calculated based on the total cases in the past, not the present number. Furthermore, numbers taken from an early sample of 41 patients yielded a mortality rate of 15%, more than our own estimate of 10%.

This illustrates that official figures are rarely accurate as to the true size and severity of an outbreak. However, by applying some simple math, we can still figure out the overall numbers. We may be off by a quite a lot, but the overall calculated trend and severity will be sufficiently accurate to take reasonable precautions. If officials understate the size of the outbreak by half, we're only off by 2 days in our projections. If officials understate the mortality rate, we can calculate our own numbers, or dig down to find more reliable numbers.

We don't have to know exactly how and when things happen, nor do we need to know the exact figures. It's still possible to figure out whether or not an outbreak is contained. We can also figure out roughly how dangerous it is. In this particular case, the numbers indicate that the outbreak is neither contained nor benign.

By I. Columbina, ad vivum delineavit. Paulus Fürst Excud〈i〉t. - 1. Johannes Ebert and others, Europas Sprung in die Neuzeit, Die große Chronik-Weltgeschichte, 10 (Gütersloh: Wissen Media, 2008), p. 197. https://books.google.co.uk/books?id=3DVH8dVGkX0C&pg=PA197 2. Superstock: Dr. Schnabel of Rome, a Plague Doctor in 1656 Paul Fuerst Copper engraving (Stock Photo 1443-1112), Public Domain, Link