For example, being on the same bus with someone meant that everyone on the bus at the same time – and probably some more besides – got counted. And anyone who had sat in that seat earlier in the day. A cashier, taking money from a customer and making change, counts – and a lot of them would do that with more than 100 people a day.

As I said repeatedly, this deliberately based the decision on a worst-case set of calculations. The fact that the results obtained line up with those deriving from the population ratios technique (also using worst-case assumptions) suggests that it is at least reasonable for a back-of-the-envelope calculation upon which to base a decision.

I also assume in those calculations that every possible encounter with Covid-19 results in infection, and we both know better than that. It might be 10% or even less.

Thanks for keeping me on my toes, though, especially on something as important as this.

BUT CoViD-no19 is already out there, so better to take precautions.