Among the many mysteries that remain about COVID-19, the disease caused by the new coronavirus, is why it hits some people harder than others. Millions of people have been infected, but many never get sick. Those who do can experience an ever-expanding array of symptoms, including loss of smell or taste, pink eye, digestive issues, fever, cough, and difficulty breathing. Although the elderly, those with pre-existing conditions such as heart disease, and men are most likely to suffer severe complications, hundreds of young and previously healthy people have died from the disease in the US alone. In recent weeks, researchers have begun asking whether genetics could influence the severity of symptoms.