In biology, a virus is a microscopic acellular infectious agent that contaminates all kinds of organisms and can only reproduce within the cells of other organisms.
Viruses spread in many different ways, and each type of virus has a way of transmitting itself. We call transmission vectors the living organisms that transport them from one person to another, from an animal to a person or vice versa. The vast majority of viruses are too small to be observed with an optical microscope, which is why they are called sub-microscopic.
Coronaviruses are a wide family of viruses and some of them have the ability to spread from animals to humans.
They produce clinical pictures that range from a common cold up to more serious diseases, as it happens with the coronavirus that is currently blighting us in a pandemic degree and that causes severe acute respiratory syndrome (SARS-CoV).
The new coronavirus is called SARS-CoV-2.
The disease that causes SARS-CoV-2 is called COVID-19.