It seems like every year brings a new outbreak of sickness.Recent research tells us how diseases spread, from person to person.And it also gives us an idea how we can spread something better than diseases.          An author called Malcom Gladwell recently published a book explaining how the process works.We usually think of an epidemic   as a force of nature that rolls over anyone in its way.In fact, it starts with a single person or very few people.These people travel around and infect   small groups in different places.When enough of these groups are infected, then the disease suddenly seems to be everywhere.Gladwell also found that the process of infection was not just limited to disease? It also affects the world of ideas.          The process can be seen in books and fashion.So called  _ are not pushed towards the public.They spread through hundreds of small reading groups until the day when everybody you know seems to have a copy.A group of young people may decide to wear an item of clothing simply because no one else is wearing it.Designers who monitor street fashion then pick up the idea and spread it.Finally everyone is wearing it.          New York is often described as an unfriendly place.People are too busy looking after business to look after each other.In the early 1990s, one unknown person decided to perform at least one kind act a day.This caught on with his or her friends.The newspapers noticed the trend  .New York became full of people smiling and carrying each other's bags.          The success of trends like this fits in with other social phenomena  .One is the 80/20 rule.This was invented by economists who noticed that in any situation 20 percent of the people did 80 percent of the work.Another is the "bystander problem".Psychologists noticed that in accidents where a large number of people were around, no one stepped forward to help.Each person supposed that someone else would do something.When there were less people present, more of them decided to offer help. What all this proves is the power of individuals   and small groups.The "epidemic model" could be a great way of making a business grow or spreading an idea.A small start can make a big difference. According to the passage, we know   _  .
The "epidemic model" doesn't exist nowadays. The "epidemic model" plays an important role in making a business grow or spreading an idea. The "epidemic model" came into being in the early 1990s. The "epidemic model" is a book written by Malcolm Gladwell.