Corona viruses are a group of Coronavirus 2020 Psych Nurse strong shirt. The have protein spikes on their surface. When seeing a corona virus in an electron microscope, it resembles a crown. And corona means crown, thereof the name. This is exactly what a coronavirus is. There are a lot of different viruses in this group, some of them only in animals, a few both in animals and humans, and some only in humans. In humans the common cold is a corona virus. Also the SARS and the MERS viruses are corona viruses.
When a virus has circulated in the human population Coronavirus 2020 Psych Nurse strong shirt, the population gets immunity against it. We even have a partial immunity against the seasonal flu. The seasonal flu changes its main antigens, which makes us ill with the new flu strains every year. The flu is not a corona virus, I only use this as an example. But when a virus in animals mutates, making it able to infect humans it is a completely new virus in the human population. We have no immunity against any of its antigens. This renders us very vulnerable of such a virus. That was the case with the Swine flu.