Preventing the spread of the virus that causes COVID-19 is key to slowing the pandemic. People who have symptoms or who have suspected or known exposure to the virus, should practice self-quarantine or self-isolation. But what do the terms mean, and which should you do? Dr. Clayton T. Cowl, a pulmonologist and chair of Mayo Clinic's Division of Preventive, Occupational and Aerospace Medicine, says that the terms are different, and people should know which one is the best option for their situation.