Feces of people with mild COVID may harbor viral genetic material months after infection | Information Center
The research team took advantage of an early clinical trial launched in May 2020 at Stanford Medicine of a possible treatment, interferon lambda, for mild COVID-19 infection. Trial participants were monitored to track changes in their symptoms as well as the degree and location of viral shedding. Fecal samples were taken from participants at specific times during the trial.
The researchers relied on the lambda interferon trial because the participants were less ill than hospitalized patients who were the subject of many other investigations at the time. They wanted to track what was happening in the majority of patients – those with mild disease.
Bhatt and his colleagues analyzed samples from 113 people at different times after infection. They found that about half of people with mild to moderate cases of COVID-19 shed viral genetic material in their stool within a week of testing positive for the SARS-CoV-2 virus. About 13% of people still excreted viral RNA four months later, after clearing the virus from their airways, and nearly 4% had viral RNA in their stool seven months after their initial infection.
Fecal excretion was also correlated with persistent gastrointestinal symptoms of the virus, including nausea, vomiting and abdominal pain.
“It’s unclear why some infected people have gastrointestinal symptoms,” Bhatt said. “But other coronaviruses are known to infect the gut of animals, so the idea of continued infection is not far-fetched.”
Researchers were unable to isolate enough viral RNA to determine which viral variant had infected the participants, or to show conclusively that samples isolated from any given individual at early and later time points were of the same strain. But because the samples were collected relatively early in the pandemic, reinfection with a second strain or variant during the study was likely unlikely, the researchers say.
The findings have implications for wastewater monitoring that researchers and governments use to infer the number of COVID-19 cases in cities and counties across the country.
“We are clearly seeing large and increasing amounts of the omicron BA.2 subvariant in wastewater nationwide,” Bhatt said. “At the same time, there have been lay reports that omicron is more likely than previous variants to cause gastrointestinal symptoms. So is this increase in sewage really proportional to the number of people infected? Or are more people shedding the virus in their feces longer?”
Understanding the dynamics of viral infection and shedding is critical to planning, Bhatt argued.
“It’s hard to interpret wastewater monitoring if we don’t understand the biology that determines who loses, when, and how much,” she said. “At the start of the pandemic, many clinicians decided that SARS-CoV-2 did not infect the gut, and that was dangerous to our understanding.”
The research was supported by the American Association for Cancer Research, the National Science Foundation, the National Institutes of Health (grants R01 AI148623, R01 AI143757, and UL1TR003142), a Stanford ChemH-IMA grant, and a Dean’s Postdoctoral Fellowship from Stanford.
Other Stanford authors are senior biostatistician Alex Dahlen, PhD; Haley Hedlin, PhD, Associate Director of Clinical Trials Program, Quantitative Sciences; undergraduate student Ryan Park; graduate students Alvin Han and Danica Schmidtke; postdoctoral fellows Renu Verma, PhD, and Karen Jacobson, MD; Julie Parsonnet, MD, Professor of Medicine and Population Health and Epidemiology; Hector Bonilla, MD, clinical associate professor of infectious diseases; Upinder Singh, MD, professor of medicine and microbiology and immunology; Benjamin Pinsky, MD, PhD, associate professor of pathology and medicine; Jason Andrews, MD, associate professor of medicine; and Prasanna Jagannathan, MD, assistant professor of medicine.