In the absence of widespread testing, each of our individual levels of being infected is a probability function, which at any given time shows a peak at some percentage figure, depending on our risk factors. Let's say that in general those peaks range from about 0.01% to 5%. I hope they aren't much worse than a few percent, but we should all act as if our own is much higher than that. 100%, even. If we add up the entire area under our individual function, it also sums to 100%, since there is a 100% chance that we are somewhere on it. The sum total of all our collective probability function peak values is the number of people who are infected  the total active cases, including the asymptomatic  at any one time. If we are all at 0.1%, then 1 in a thousand people are infected. (Currently  the end of 23rd April  almost 3 in a thousand Americans are known active cases. We can confidently state that many more are infected. 50,000 have died.) R, the reproduction rate, tracks whether that number will be larger tomorrow or smaller, and is a measure of the risk of infection level in the population at large. Every change in our behavior affects our individual probability functions, and, as a consequence, R. Small individual changes in behavior affect our probability function, and can result in the number of infected people rising (or falling) by a fraction of a person. Multiplied across millions of people, however, they can result in hundreds of thousands of infections  and thousands or tens of thousands of deaths. They can also prevent those infections and deaths if they lower our probability functions. We will have informal and formal changes like this. The informal ones are due to our own calculations, our own gambles, our own attitudes about what is risky, and how those individual perspectives and decisions based on them change over time. It is critical to try to manage these individual trends so they don't run out of control while we try to develop formal changes. The formal changes are the policies adopted and to some degree enforced by governments and public health organisations. They need to be concise and measured, wellconsidered and manageable. We must be able to measure and manage their effect. Yes, they will result in more infections. But can we then minimize the mortality rate by early detection and topnotch care? And is the slight increase in deaths, before we could possibly vaccinate or protect those people, worth the level of "return to normal" that produced them? Remember that the goal is to outwait the virus. To minimize its impact  its interference in our lives at the levels of infection and disruption  until we can begin to actively disrupt its progress. Ideally this would be through an effective program of vaccination. But we do not know if that will even be possible yet. (It probably will be, and will probably be fairly well accomplished by late 2023.) In the worst case scenario (well, not counting it becoming more virulent or more deadly), we have to just slow it down enough that not only can every sick person get the best possible care, but that we come up with new and better methods of treatment, reducing the mortality rate to something that really is acceptable. The best case outcome in the worst case scenario is that we isolate and quarantine the virus to extinction, but that is highly unlikely. PS The first sentence is really the gist of what I was trying to say and explore. But I kept interrupting myself with other thoughts. The first sentence is the key. In the absence of testing, whether we are infected or not is similar to a quantum phenomenon. We are all Schrodie's kittens in one giant, horrible, thoughtless experiment. 4/23/20 © Huw Powell
