Coronavirus: Interim summary

To summarize the thoughts contained in the last several posts:

1. Points of equilibrium. The spread of the virus proceeds, in a given environment to points of equilibrium. These are points at which the number of new cases is balanced against the number of infected people who are no longer capable of passing the virus to someone else.

2. Conditions. There are only two conditions that need to be satisfied in order for the points-of-equilibrium model to be valid: resistance to spread of the virus must increase as the virus spreads, and the rate at which infectious people drop out is proportional to the total number of active cases.

3. Interventions. The points of equilibrium, and thus the numbers infected and infection rates can be altered by interventions. Whatever interventions exist in a particular environment at a particular time determine the point of equilibrium.

4. When interventions change, new points of equilibrium are established. The number of new cases will increase or decrease to accommodate the new equilibrium point. The default equilibrium point is not the point of herd immunity or the condition where everyone is eventually infected.

5. There are two competing hypotheses: that interventions affect the ultimate number of people of infected, and that they do not. If the former case is true, the goal of interventions is to limit the total number of people infected, if the latter is true, the goal is to control the rate of spread, with the idea of limiting deaths occasioned by inadequate healthcare resources.

6. The point of equilibrium model is consistent with both hypotheses.

7. Hydroxychloroquine is rational therapy that is not strictly a "cure" but has a reasonable mechanism to limit disease severity in infected persons.

8. Loosening mitigation efforts will result in an increase in case rate as a new equilibrium is reached, and this will happen regardless of when such actions are taken.

9. The actual peak of the epidemic occurs several days, roughly equal to the incubation period, before the observed peak.