When the virus first emerged in China, epidemiologists scrambled to understand how it spread from person to person. One of their first tasks was to estimate the average number of people each sick person infected, or what epidemiologists call the reproductive number. The new coronavirus turned out to have a reproductive number somewhere between two and three. It’s impossible to pin down an exact figure, since people’s behavior can make it easier or harder for the virus to spread. This averaged figure can also be misleading because it masks the variability of spread from one person to the next.

Source: New York Times June 30, 2020 04:01 UTC