Transmission of viruses from one species to another is not unusual in nature. Despite this, evolutionarily successful transmissions are rare. Such events can cause pandemics and are followed by host–virus coevolution procedures that can increase the fitness potential of viruses. In this perspective article, I recognize eight main types of trans-species viral transmission. I consider two of them as evolutionarily successful, explaining why coronavirus SARS-CoV-2 could be one of them.
- Molecular evolution
- Natural selection