R0 is the basic reproductive ratio of an infection. It predicts how many new instances of infection are caused by one existing case of infection. It is also the latest ingredient in the pandemic cookbook to be seized upon by the government and used incorrectly to try and maintain the lie, and keep everyone believing that the government’s response is in some way (OK, in any way) correct.
Emperor Wannabe-Winston Johnson has been throwing the R0 number around with his usual vagueness, proclaiming that it has to be brought down to less than 1 because that’s the latest focus and all that matters.
R0 has utility in predicting the spread of infection and its mathemtical function is exponential, so if you use a factor of 2 you get the 2,4,8,16,32,64…sequence you will remember from maths lessons. Increase the factor to 3 and the sequence becomes 3,9,27,81, 243, 729. This wide diference by just the sixth value in each sequence is why people get very uptight about the R0 value.
However, R0 is not all it is cracked up to be, especially when used incorrectly. Firstly, it is not a constant. It is the output of predictive models and based upon statistics. It is used when talking about biological pathogens but itself is not a biological value.
Next, it is dimensionless, in that it has no comparator or unit of measure. This is crucial and a mistake made by many people who quote R0 as a rate, which it is not, rather than a ratio, which it is. For example, you are travelling at 26. How fast are you going? ’26 what?’ you say – correct, without some unit of measure you don’t know and can’t answer. 26 miles per hour is somewhat different to 26 metres per second (which equates to 58 miles per hour) and very different to 26 kilometers per minute (which equates to 969 miles per hour).
R0 seeks to quantify how many other people will be infected by one person but it is very easily distorted by any number of factors, such as the health of the population at large; any existing immunity; the virulence of the pathogen; its infection cycle and even the weather conditions if these affect the pathogen’s method(s) of transmission.
So with all this in mind, while R0 is relevant it is neither an absolute nor relative value. For example, chickenpox has an R0 in the range 10-12 and Ebola has an R0 in the range 1.5-1.9. Which would you rather have?
This leads into the main error that Emperor Wannabe-Winston Johnson is making: trying to use the R0 as a measure of severity or frequency, when it is neither because it is dimensionless. Frequency and severity are relevant as they are the two fundamental components of risk: frequency being how often something is likely to happen and severity being how bad that something could be. A higher R0 value does not make a pathogen more dangerous or virulent: again, use the chickenpox and Ebloa R0 values or compare Ebola with seasonal flu – A(H1N1)/A(H3N2) – which has an R0 in the range 0.9-2.1, so these two are very similar in respect of their R0 values but – again – which would you rather have?
SARS-CoV-2’s R0 is generally accepted to be in the range 2.25-2.75. We have previously referenced the very comprehensive and authoritative modelling undertaken by Oxford University’s Evolutionary Ecology of Infectious Disease group. Their analysis suggests between 36% (R0 2.25) and 40% (R0 2.75) of the population had been exposed to SARS-CoV-2 as of 19th March. Allowing for the proportion of the population at risk of severe infection (0.1%), this increases the figure to 68%. That’s over two-thirds of the population having been exposed to the virus by 19th March. When you consider SARS-CoV-2’s very low minimum infectious dose and asymptomatic characteristic, you can pretty much deduce that most of the population have had the virus.
Before ‘lockdown’ was announced, most people had already had SARS-CoV-2, rendering ‘lockdown’ unnecessary and pointless. This is substantiated by the peak deaths having occured on 8th April, which puts the peak infections somewhere around 18th March. Not far off the 19th March then and again, before ‘lockdown’ was imposed as the putative correct course of action.
Continuing to quote an R0 value and use it as a condition for ending this insanity serves no purpose. It is yet another example of the fearfest where the government makes out the situation is far worse than it is, wheeling in ever new ‘dangers’ and more potential issues that will have to be overcome. Anything to keep the lie going for a bit longer and save their utter failure from being unmasked.
The R0 is dynamic and naturally changes through the course of an infection’s life cycle. The greater the proportion of the population who have had the virus, the smaller the remaining proportion becomes, limiting the virus’ capability to continue to survive. In effect it has to work harder to try and find new hosts and this is reflecting in the R0 ratio rising in the latter stage of the life cycle. Think of it as a contestant in a game show that has 2 minutes to find x number of gold stars: as the clock ticks down, the contestant runs around faster & faster, desperately trying to grab as many as they can before time runs out.
At the same time, its increased transmission comes at the expense at reduced virulence. Once herd immunity has been achieved, a virus usually weakens and this process continues until its life cycle comes to an end. Again, think of the game show contestant who in their desperation and focus on the clock casts off some of the items they have already collected in order to be able to move quicker.
To use this life cycle to your advantage, i.e. to exploit the virus’ reduced virulence, you do not hide people away but rather allow the virus’ life cycle to run its course. Yes, shield those at high risk and certainly don’t congregate your sick and those caring for them in confined spaces for sustained periods of time (high viral dosage and high viral load) but apart from these requirements, allow everyone else to carry on regardless, especially as most of them have already had the virus.
The government’s response is based upon two assertions: 1. nobody must be allowed to get the virus becuase 2. if you get it you will die and kill the NHS
whereas in reality 1. most people have now had the virus and 2. most did not die.