[nomadking]

There is still a large pool of people who have yet to become infected. Those that have become infected and have recovered can still transmit it to somebody who is still susceptible. It can only disappear if there is no longer the possibility of it having access to a viable host in order to prolong its "life" and continue the chain of infections.


I've previously used the comparison with dog fleas. Think of the dogs as the as yet uninfected, and humans as the immune. Humans can pick up dog fleas but they are unable to survive and reproduce on human blood. There is a period of time whilst the dog flea is still alive on the human, where it can jump to another human or another dog. If it jumps to another human, it is at risk of starving and dying out. If it jumps to another dog, it now has the opportunity to survive and reproduce, and carry on existing.