How a virus like a coronavirus jumps from animals to people
The Centers for Disease Control and Prevention estimates that three out of every four new infectious human diseases — including coronavirus diseases like COVID-19 — jumped from another species. Viruses are trying to infect new hosts all the time, but there are a lot of barriers that they need to get through before that can happen. First, a new virus needs to come in contact with humans, then overcome the body's natural defenses, and finally spread between people. But at any point along the way it can be stopped dead in its tracks. Here's what needs to happen for a virus to jump from animals to people.
