London is more densely populated than Yorkshire. London currently has one in 100 infected. Yorkshire has one in 125, a significantly lower figure in reality. Yet we are told the r number is significantly higher I Yorkshire than it is in London. So in a less densely populated area with fewer infections the R number is higher than a more densely populated area with more infections? Eh?
I’m guessing the R rate is an indication of the rate infections are falling and not a reflection of actual infections. Yorkshire has had steady rise/steady fall compared to London which had a huge spike- starting at a much higher level the potential fall is much quicker.
The R number is the average number of people that get infected by a single infected person. A lower R rate will be as much influenced by how well the restrictions are observed as by the infection rate and population density. I don't think the evidence suggests a better compliance in London than Yorkshire so I agree that it's really hard to explain. I'm convinced that the figures were massaged during the abortive tiered system in the autumn, to allow more freedom in London. But with a general countrywide lockdown, there's no point.
It’s not a snapshot of how many infections, it’s the growth rate of infections. like it has been from the start.
Not quite, there is no dependence on time so it's not the rate of change in infection numbers. See my post above. Incidentally there have been questions about why we need lockdowns for COVID but not for the annual flu. This is explained by R. In a society with no restrictions (ie normal life), COVID has an R value of about 3 whereas flu is about 1.3 hence if the older more and vulnerable are vaccinated then the NHS can cope with the annual flu. Not so with COVID. What's worrying is that the Kent variant is 70% more transmissible so it has an R of about 5. Just for reference, the 1918 Spanish flu had an R of 1.8.
As others have said, R is the rate of infection - or the number of people each infected person will infect. With any disease, this varies between 0 and R0 - the initial rate of infection of a new illness in a population with no immunity. From R and the reproduction cycle, you can estimate how many infections will be present in the population after periods of time: e.g. London. 1% infected. R = 0.9. Cycle = 7 days. After 1 week, the number of new infections will be 0.9%. After 2 weeks, the number of new infections will be 0.81%. This is good Yorkshire. 0.8% infected. R = 1.1. After 1 week, the number of new infections will be 0.88%. After 2 weeks, 0.97%. This is bad.
Correct, this is why the R value needs to be less than 1, otherwise infections are rising. When sufficient people are vaccinated (assuming vaccinated people don't transmit) so that an infected person will be unlikely to meet a person who is vulnerable, the R number has fallen so low that the infections die out, this is "herd immunity".
