The results suggest that knowing the so-called viral load — the amount of virus in the body — could help doctors predict a patient’s course, distinguishing those who may need an oxygen check just once a day, for example, from those who need to be monitored more closely, said Dr. Daniel Griffin, an infectious disease physician at Columbia University in New York.

Tracking viral loads “can actually help us stratify risk,” Dr. Griffin said. The idea is not new: Managing viral load has long formed the basis of care for people with H.I.V., for example, and for tamping down transmission of that virus.

Little effort has been made to track viral loads in Covid-19 patients. This month, however, the Food and Drug Administration said clinical labs might report not just whether a person was infected with the coronavirus, but an estimate of how much virus was carried in their body.