"In essence, what the study of 10 million people confirmed is what many people, doctors, scientists and World Health Organization already suspected. "Like the common cold and flu when a person is infected with the virus they are only infecting others when they have symptoms: cold, runny nose, coughing, aching, sneezing, fever, congestion etc; hence, when a person has an illness they should isolate to not spread the virus. However, when a person has no external symptoms of the virus, just like the cold and flu, they are not a risk of transmitting the virus to others." Link in comments.