Study Tracks Course of COVID Infection, Transmission in Individual Patients

TUESDAY, May 3, 2022 (HealthDay News) -- So-called "superspreaders" aren't necessarily carelessly mixing with throngs of people.

Instead, a new study finds, some people with COVID-19 infections shed the virus for just a few days, while others do so for up to nine days.

"Based on that finding, we predict that those people who are shedding virus for more than a week are going to be at much greater risk of transmission than someone who only has live virus detectable for a day or two," said study co-author Christopher Brooke, a microbiology professor at the University of Illinois.

Co-author Pamela Martinez stressed that "this is a very key finding."

Martinez, a microbiology and statistics professor, said, "We assume that superspreaders are less cautious or are in contact with more people. This shows that intrinsic infection dynamics also play an important role."

In the study, the researchers started taking daily nasal and saliva samples from 60 participants, aged 19 to 73, within 24 hours of a positive COVID-19 test. The patients were followed for up to 14 days.

Along with finding differences in how long infected people shed the virus, the study showed that viral genome loads that are detectable with PCR tests peaked much earlier in saliva samples than in nasal swabs.

This suggests "that saliva may serve as a superior sampling site for early detection of infection," according to the authors of the study published April 28 in the journal Nature Microbiology.

The investigators also found no significant links between people's symptoms and the course of infection. It's often assumed that patients with more symptoms are likely to be more infectious, but that may not always be true, Brooke said.

The implications of this finding may be limited because all of the participants were either asymptomatic or had mild symptoms, the researchers noted.

"Overall, this study helps explain why some people are more likely to transmit SARS-CoV-2 than others," Brooke said.

The study is the first to follow people with COVID-19 infections over time and to compare results from different methods of testing, according to the authors.

"We capture the most complete, high-resolution, quantitative picture of how SARS-CoV-2 replicates and sheds in people during natural infection. There are no other data like this," Brooke said.

More information

For more on COVID-19, go to the U.S. Centers for Disease Control and Prevention.

SOURCE: University of Illinois Urbana-Champaign, news release, April 28, 2022