The 80-20 Rule, also known as the Pareto Principle, is a pattern that’s seen in many groups of people. It means that 20 percent of the people usually have a big influence on 80 percent of the final result. This rule applies in various ways: 

In most societies, around 20 percent of employees do about 80 percent of the work. Similarly, 20 percent of criminals are responsible for about 80 percent of crimes. When it comes to accidents, roughly 20 percent of drivers cause around 80 percent of them. Even when it comes to beer, around 20 percent of beer drinkers consume about 80 percent of the beer.

The same principle applies to virus epidemics, but the ratio is even more extreme. A small percentage of infected people do most of the “work” in spreading the virus. For example, in the early days of AIDS in the United States, many cases could be traced back to one flight attendant who had sexual contact with over 2,500 people, significantly contributing to the virus’s spread.

In social epidemics, a certain few people also play a crucial role in speeding up the spread. These individuals often have special social connections or a remarkable personality. In many cases, it’s just a handful of key people who cause epidemics.