“R0 = βN/( α + b + v) In English: The evolutionary success of a bug is directly related to its rate of transmission through the host population and inversely but intricately related to its lethality, the rate of recovery from it, and the normal death rate from all other causes. (The clunky imprecision of that sentence is why ecologists prefer math.) So the first rule of a successful parasite is slightly more complicated than Don’t kill your host. It’s more complicated even than Don’t burn your bridges until after you’ve crossed them. The first rule of a successful parasite is βN/( α + b + v).”

— Spillover: Animal Infections and the Next Human Pandemic by David Quammen a.co/8FU04W1