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Old 9th May 2020, 12:23
  #6415 (permalink)  
Join Date: Oct 2002
Location: West Wiltshire, UK
Age: 67
Posts: 390
Originally Posted by golder View Post
Yet every corner, the whole of the UK and australia gets the flu. That is a less contagious base RO than covid. There is no where it won't get to in time. Time to travel is the difference, unless something stops it. Wishes and prayers may not work.
However, we're talking about the rate of infection, and the fact that this is faster in densely populated areas than it is in sparsely populated areas. Ultimately most infectious diseases end up being pretty much everywhere eventually, but at any instant during the active spread of disease phase there will always be a pattern, that follows well-understood principles that define how quickly infection spreads. Not sure why this seems so hard a thing to grasp, as it seems pretty intuitive. One case in somewhere like London is very likely to cause a larger number of subsequent cases in a given time period as one case in somewhere like the middle of Dartmoor, simply because more people are likely to be exposed to each case.

It's easy enough to show this by just looking at the impact of changing R is (R being dependent on population density, as well as other factors). For 5 generations of infection from a single case (roughly 20 to 25 days), with R at 3 there would be around 243 cases. If R reduces to 2, because people are more spread out within a population, then after 5 generations from a single case there would be around 32 cases, a significant difference.

The whole principle behind social distancing is to spread people out, so the risk of infection reduces, which is reflected in a reduction in R, the effective reproduction number. It doesn't matter whether social distancing is an enforced measure, or a natural one as a consequence of population density, it has the same impact on reducing R.
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