COVID-19 is caused by the SARS-CoV-2 virus. First 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 behaves differently.
As with other respiratory illnesses, COVID-19 infection can cause lung damage and breathing problems. But it also attacks other parts of the body, including the heart and blood vessels. It also seems to trigger inflammation and blood clots in some people. Because it had never been seen in humans before, at first no one had existing immunity to it (that is, an ability to naturally fight it). Today, over half of Americans have had COVID-19 at some point, according to estimates. Vaccination has helped protect communities, too.
But we are still learning about the virus. For example: