R0 is part of an ODE rate constant in the SIR epidemiological model

The SIR model divides the population into 3 groups. S = susceptible - people who able able to be infected. I = people who are currently infected and R = removed - people who are either immune or have died. Each group is represented as a proportion so S+I+R = 1.0

We can define ordinary differential equations to calculate how these change over time. These ODEs need a rate constant. In the simplest model we have:

dS/dt = -beta.I.S/N
dI/dt = +beta.I.S/N - gamma.I
dR/dt = gamma.I

The rate constant beta = R0/tau, where R0 is the number of people one infected person will infect during the period they are infectious and tau is the length of time that they are infectious for.

R0 stems from the behaviour of those who are infected. It is the key factor in the rate of growth of the pandemic. R is the proportion of the population who have died or have recovered.

Now, recall that only about one in five of those who exhibit covid symptoms have been self isolating. The effect of the behaviour of the thankfully small proportion of the population who fall into the I group has huge implications on the rest of the population in the S and R groups. From my point of view the key isn't fiddling with whether the pubs close at 10 or 11 but how we can enforce/encourage more considerate behaviour from those with symptoms.

Everyone is entitled to their own view. I was just trying to work out what a normal range of responses would be.

Posted By: Timmy_Goat on October 13th 2020 at 15:30:55

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