COVID-19 is an illness caused by a virus that infects humans and can involve several organs. Discovered in 2019, the new coronavirus quickly spread around the world.
Although it’s part of the same family of viruses that cause the common cold, the virus that causes COVID-19 is very different. Because it had never been seen in humans before, no one had existing immunity to it (that is, an ability to naturally fight it).
We are learning more about the virus every day. For starters, we don’t yet know: