COVID-19 is the disease caused by SARS-CoV-2, a type of coronavirus. Coronaviruses are a family of viruses common in humans and many different animals. Viruses in this family can cause respiratory illnesses ranging from the common cold to more severe diseases.

Some cases of COVID-19 can be mild, but others can be more severe and sometimes deadly—especially for older adults or those living with other chronic health conditions.

The original virus that causes COVID-19 has mutated into different strains called variants. Different variants may spread more easily, may cause more serious disease, and may not respond as well to treatment. 

Last Updated September 2023