How Risky Is Your Gathering?

In a time of alarm over virus transmission, how dangerous is a gathering of people? This post from Tyler Cowan's blog features a risk assessment calculator, giving the probability that someone at an event is carrying the Wuhan Coronavirus, based on the size of the event and the number of carriers nationwide.

It's reassuring to see that gatherings of up to about 30 people are pretty safe even if there are 100,000 carriers nationwide. This particular calculator is scaled for the USA, with 300 million people. For smaller countries, I think it would scale by reducing the number of carriers for a given risk level in proportion to population. I think.

Prince Prospero could have used this calculator when making up the guest list for his famous Masque. He invited a thousand other nobles to his event, but at the time the number of Red Death carriers in his kingdom was extremely high relative to population, so naturally the party guests got infected. If he had limited himself to a small dinner-party he might have made it through the epidemic alive.