“The scale of an outbreak depends on how quickly and easily a virus is transmitted from person to person. While research has just begun, scientists have estimated that each person with the new coronavirus could infect somewhere between 1.5 and 3.5 people without effective containment measures.”
Read More: https://www.nytimes.com/interactive/2020/world/asia/china-coronavirus-contain.html?smid=nytcore-ios-share#transmission