The concept of a personal Rp (a personal reproduction number)
A population is made up of individuals. And individuals have a wide spectrum of behaviours or characteristics. The population may be said to have an average value for R (called R0 in a completely susceptible population) and that value is useful for examining and predicting the course of an infection. For Covid it is probably about 2.2. But it may be that an infection will travel through the population via individuals whose personal characteristics are more favourable to the infection than all the other individuals in the population. Those individuals could be said to have a high personal infection ratio, Rp. For Covid it may be 3.0 or 4.5 depending on the individuals behaviour and circumstances. They might be individuals who live in a big family or in a dormitory or a captive space like a prison or care facility, or like to visit crowded places like pubs and restaurants and shopping centers, working where social distancing is difficult or the environment is cold, travelling on public transport, being careless with social distancing, being non-compliant with restrictions or not wearing a mask in risky situations. On the other hand a retired single person living at home who is compliant with restrictions and whose children do the grocery shopping and leave it at the front door for them will have a very low Rp.
The effect of networks in the community. It seems logical that once the virus reaches a high Rp individual it would spread easily via the contacts that that individual has with other high Ri individuals. The netwok. Like water taking the path of least resistance through lower lying areas, the virus would take the path of least resistance via high Rp individuals. In network theory these individuals would be seen as a network. There are probably many networks of high Rp individuals and they each have the potential to easily spread the infection. But nothing happens until one of those individuals is infected. At that point 'nothing to see here' becomes a cluster of infections spreading via the network. A retired single person living at home who is compliant with restrictions may become infected, but will likely not infect others (low Rp).
The effect of networks in the community. It seems logical that once the virus reaches a high Rp individual it would spread easily via the contacts that that individual has with other high Ri individuals. The netwok. Like water taking the path of least resistance through lower lying areas, the virus would take the path of least resistance via high Rp individuals. In network theory these individuals would be seen as a network. There are probably many networks of high Rp individuals and they each have the potential to easily spread the infection. But nothing happens until one of those individuals is infected. At that point 'nothing to see here' becomes a cluster of infections spreading via the network. A retired single person living at home who is compliant with restrictions may become infected, but will likely not infect others (low Rp).
