How Has COVID Viral Shedding Changed Over Time? – Verywell Health

Key Takeaways

Since the pandemic began, researchers have used several metrics to try to track the infectiousness of COVID-19. One mainstay is viral shedding, which is the subject of a new study that aims to determine just how long kids are infectious after being diagnosed with COVID-19.

The study, which was published in JAMA Pediatrics, looked at data from 76 children between the ages of 7 and 18 who tested positive for COVID-19. The researchers took throat swabs during five home visits over 10 days to track viral shedding over time. They determined that most kids were infectious up through day three of their infection, although 18.4% of kids were still infectious on day five. Three kids (or 3.9% of participants) were still infectious on day 10.

The results raise a lot of questions about viral shedding and where things stand with going back to school or work after having a positive COVID-19 test result. Infectious disease experts explain.

Viral shedding means that a live virus is still detectable for a period of time after someone is infected with an illness, William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, told Verywell.

Viral shedding suggests that, during the period of time that someone is shedding the live virus, that they might be contagious or able to spread the virus to others, he said. Over time, the amount of virus that people shed drops.

The way viruses work is that they invade our cells, multiply and then can spread to other cells in the body or to other individuals, Thomas Russo, MD, a professor and chief of infectious diseases at the University at Buffalo in New York, told Verywell. People use the term viral shedding to talk about when an individual is expelling a virus into the air.

In general, viral shedding indicates how potentially infectious someone isbut not all viral shedding can make people around you sick.

If you shed the virus at low levels, you might not be infectious, Russo said.

Study coauthor Eran Bendavid, MD, associate professor of medicine at Stanford University, told Verywell that he and his colleagues wanted to help determine how long kids are infectious with COVID-19 after they get sick. But he also said that viral shedding alone is a poor measure of how infectious someone isthats why his study also looked at viral shedding that also caused evidence of infection in cell cultures.

Viral shedding is what a PCR test would pick up, and it does not tell you, in isolation, if the virus is capable of causing disease, Bendavid said. Why do researchers continue to look at it? Because its easy to measure. Infectivity is much more informative but hard to measure. Thats why our study was important.

Other data has been collected on different aspects of viral shedding. A study published in Open Forum Infectious Diseases in August 2020 found that people with COVID-19 with higher levels of viral shedding were more likely to be older, have pre-existing chronic conditions, and have more severe forms of the illness than those who shed less of the virus. But it didnt track the length of time people were infectious.

Another study published in the journal Emerging Infectious Diseases in 2022 found that adults who had the Omicron COVID-19 variant shed the most virus between days two and five after they were diagnosed. The researchers also found that infectious virus was detected up to nine days after people were diagnosed.

But Schaffner said that theres no clear information on how viral shedding has changed over the course of the pandemic, given that studies on the virusincluding viral sheddingwerent as robust early on.

Early in the pandemic, we were using PCR tests, which could detect pieces of the virus, he said. Those could have been dead soldiers. Some studies showed that people could be PCR positive for a week, two weeks, and sometimes even longer after they recovered, even though its unlikely they were infectious then.

Bendavid agrees that its hard to know how viral shedding has changed over time with the pandemic.

There are some reasonable implicationsfor example, that as the disease has become more mild, that shedding has decreasedbut we do not actually know that, Bendavid said. He also pointed out that his study found that children who were unvaccinatedand likely had a more intense illnessshed virus for the same amount of time as those who were vaccinated.

The Centers for Disease Control and Prevention (CDC) currently suggests that people who test positive for COVID-19 isolate until five days after their symptoms started, with isolation ending after someone has been fever-free for 24 hours without the help of medication. However, the CDC also recommends wearing a mask around others through day 10.

Despite the latest studys findings, Schaffner said that the CDC is unlikely to shorten isolation recommendations around COVID-19.

Russo agrees. With these findings, nearly one out of five kids going back to school could infect othersbut its also important to get kids back in school, he said. What protocols are we willing to maintain as a functioning society as the risk of COVID goes down, but isnt zero? We still need to figure that out, he said.

New research shows that children who are infected with COVID-19 are typically infectious through day three of their illness. However, nearly 20% are infectious through day five of their illness. If you test positive for COVID-19, doctors say its safest to follow CDC guidance and isolate for five days to lower your risk of infecting someone else.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit ourcoronavirus news page.

Kumar N, Bendavid E, Sood N. Duration of SARS-CoV-2 culturable virus shedding in children. JAMA Pediatr. Published online October 23, 2023. doi:10.1001/jamapediatrics.2023.4511

Tingting Liao, Zhengrong Yin, Juanjuan Xu, Zhilei Lv, Sufei Wang, Limin Duan, Jinshuo Fan, Yang Jin. The correlation between clinical features and viral RNA shedding in outpatients with COVID-19. Open Forum Infectious Diseases. August 2020, doi:10.1093/ofid/ofaa331

Takahashi K, Ishikane M, Ujiie M, et al. Duration of infectious virus shedding by SARS-CoV-2 Omicron variant-infected vaccinees. Emerg Infect Dis. 2022;28(5):998-1001. doi:10.3201/eid2805.220197

Centers for Disease Control and Prevention. Isolation and precautions for people with COVID-19.

By Korin Miller Korin Miller is a health and lifestyle journalist who has been published in The Washington Post, Prevention, SELF, Women's Health, The Bump, and Yahoo, among other outlets.

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How Has COVID Viral Shedding Changed Over Time? - Verywell Health