Spillover: the powerful, prescient book that predicted the Covid-19 coronavirus pandemic.

by David Quammen

HUMAN-TO-HUMAN transmission is the crux. That capacity is what separates a bizarre, awful, localized, intermittent, and mysterious disease (such as Ebola) from a global pandemic. Remember the simple equation offered by Roy Anderson and Robert May for the dynamics of an unfolding epidemic? R0 = βN/(α + b + v) In that formulation, β represents the transmission rate. β is the letter beta, in case you’re not a mathematician or a Greek. Here it’s a multiplier in the single expression that stands as numerator of the fraction, a strong position. What that means is, when β changes muchly, R0 changes muchly. And R0, your good memory tells you, is the measure of whether an outbreak will take off.