We often see a ratio expressed: deaths, as a proportion of cases. The figure is taken as a sign of how lethal Covid-19 is, but the ratios vary wildly. In the US, 1.8 per cent (2,191 deaths in 124,686 confirmed cases), Italy 10.8 per cent, Spain 8.2 per cent, Germany 0.8 per cent, France 6.1 per cent, UK 6.0 per cent. A fifteen-fold difference in death rate for the same disease seems odd amongst such similar countries: all developed, all with good healthcare systems. All tackling the same disease.
You might think it would be easy to calculate death rates. Death is a stark and easy-to-measure end point. In my working life (I'm a retired pathology professor) I usually come across studies that express it comparably and as a ratio: the number of deaths in a given period of time in an area, divided by that area's population. For example, 10 deaths per 1,000 population per year. So just three numbers:
- The population who have contracted the disease
- The number dying of disease
- The relevant time period


















Comment: Two other clear-headed reports by Dr. John Lee can be read here: