A new study in South Korea, published Thursday in JAMA Internal Medicine, offers more definitive proof that people without symptoms carry just as much virus in their nose, throat and lungs as those with symptoms, and for almost as long.

A new study in South Korea, published Thursday in JAMA Internal Medicine, offers more definitive proof that people without symptoms carry just as much virus in their nose, throat and lungs as those with symptoms, and for almost as long.