COVID-19: Duration of test positivity vs. infectiousness

Monday, September 21, 2020

Over the last several months, clinicians at WVU Medicine and around the world have learned a lot about COVID-19, including its symptoms, treatments, and transmission dynamics.

In the video below, Arif Sarwari, MD, WVU Medicine infectious diseases specialist and chair of the Department of Medicine, discusses the distinction between the duration of time a person tests positive versus the time period that person is infectious to others.

“We now know that most people who are infected with COVID-19 develop symptoms about five-to-seven days after exposure. It is at about this time that the person is most infectious, meaning able to infect others,” Dr. Sarwari said. “What we have also learned is that this infectiousness very rapidly declines, such that over the next seven-to-ten days of symptoms, you no longer transmit the virus to others as efficiently as you did at the beginning.”

This is important from a testing perspective, he added, because testing for COVID determines whether one is infected but does not assess a person’s infectiousness to others. A test may remain positive for a lot longer duration than the few short days in which most transmission occurs.

Sarwari said, “We should be able to do what we need to do based on the science that has evolved to show us that periods of transmission are restricted to the first seven to 10 days after symptom onset.”

The bottom line? Repeated testing until a patient is negative is clinically unnecessary.