Mark Handley, a scientist from UCL that I follow, seems to have worked out that 1 in 25 people in London would be infected with the Coronavirus.
I found the
mathematics of engineer Tomas Pueyo very interesting: he proposes a good method of calculating the number of infected people, simply based on the current number of deaths.
He worked out that at any point in time, the number of infected people in a region will be around 800 times the number of coronavirus deaths that have occurred in that region.
I was able to estimate that there have been about 70 deaths in Greater London so far (using
this UK map), which implies that there are 70 * 800 = 56,000 infected people in London at present. That works out to around 1 in 160 infected in London.
Tomas Pueyo's calculation is based on the mathematics of exponential growth, and the fact that it takes an average of 17.3 days for death to occur after the person is first infected. So there is a time lag to death, during which the total number of infected people in the region will further increase, as a result of exponential spread of the virus.
In other words, the number of deaths today provides a snapshot of the situation it was 17.3 days ago; but by using exponential growth equations, you can use this snapshot to calculate the estimated number of infected today.
His calculation assumes two figures: that the death rate is 1% (1 in 100 people with the virus will die), and that the rate of exponential growth of infected people is such that the total number infected doubles every 6.2 days. From these two assumptions, you can arrive at the result that the total number infected people at any given point in time is 800 times the number of deaths at that point in time.