Corona Virus
A series of write ups on the virus
Clarification
07/5/2020
More information has become available since I
started writing these articles. In particular the mortality
rate, and the way that other countries are tackling the virus.
As we are now approaching the end of lockdown the following
articles will deal with the progress.
Tracking
Tracking the number of infections in the UK is a fruitless task.
The number arrived at depends on both the number of infections
and how many people you test. If we use data from countries who
test well, like New Zealand, Australia, and S Korea we find that
the mortality rate is about 1.34%. So we can estimate
infections by 1/1.34% or about 75. Now this is what the
infections were 14 days before. So we must take the growth into
account.
If we do that for the UK we find reported cases two weeks ago
are 89 times the number of deaths today. In fact the
number of cases must be about 75 times the number of deaths. So
deriving statistics from cases in the
UK is of little value. All of these calculations use deaths.
Care home deaths
I get the UK figures from the
governments own statistics`.I take the "deaths in all
settings" number, and subtract "the equivalent figure under the
old measure" which was hospital deaths, to arrive at care home
deaths.
The Office for National Statistics publishes a care home
death figure which is far greater, although the total death
figure is similar.
R value vs Growth Factor
The government insist on quoting the "R value" (or R nought)
when determining the spread rates of the virus.
The R value is the measure of how many people one person infects
before they are free from the disease via recovery or death.
It is extremely difficult to
calculate and in my humble opinion a singularly useless
figure to track progress against the virus.
We are not told what the actual value of R is, other than "
between 0.5 and 0.9. Neither are we told what we are aiming for
other than "less than 1"
If we assume that 100 people are infecting others over a 14 day
period, then with a R value of 1, at the end of 14 days we will
still have 100 people infected. With and R value of 0.5 then 50%
would be infected.
My explanation of the R value may be too simplistic
or simply wrong. I can't check as the government publish neither
the R value figure nor the calculation method.
The government are currently (7th May) saying the R value is
about 0.7.
My stats show the growth rate is 97.08%
It seems that a method to convert growth rate to R value
raise 97.08% to the power of 14 which gives 66% or 0.66.
Close enough.
It is much easier to track the growth rate and
it is an unambiguous figure. Unfortunately, we can only derive
the infection rates as they were two weeks previously. But this
is still better tracking than infection rates from a grossly
inadequate testing regime.
We can however compare our growth rates with
other countries and gather from their experiences as they
attempt to come out of lockdown.
All of the data on the following pages use
the growth factor, but assuming my explanation
is close enough , here is a translation from Growth Rate to R nought.
Update 20/6/21
It seems that people are not infectious for th full 14 days, but
probably nearer to 7 days. Given that, it is probably more
accurate to raise the growth rate to the factor of 7 rather than
14. This would make the 97.08% growth mentioned above
equivalent to R0 of 0.81.
