Fecal Evidence of COVID-19 Raises Transmission Concerns

David A. Johnson, MD


March 18, 2020

This transcript has been edited for clarity.

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Hello. I'm Dr David Johnson, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia.

It's not news to tell you that the coronavirus, known as COVID-19, is a worldwide problem. The initial outbreak of this novel virus in Wuhan in the Hubei province of China, first described in December 2019, has since moved on to being declared a pandemic by the World Health Organization.

The classic description of COVID-19 is a respiratory illness that manifests with fever, dry cough, and dyspnea on exertion. However, we're starting to see the potential for gastrointestinal (GI) implications of COVID-19 as well. This was observed with similar viral respiratory illnesses, such as severe acute respiratory syndrome (SARS), which emerged in 2003, and the Middle East respiratory syndrome (MERS), which emerged in 2012. These infections were transmitted through contact and viral spreading via microdroplets transmitted from the respiratory tract, as is also alleged for COVID-19. A fair percentage of patients with MERS and SARS developed GI symptoms later in the course of the disease.

In a recently published single-center case series of 138 consecutive hospitalized patients with confirmed COVID-19, investigators reported that approximately 10% of patients initially presented with GI symptoms, prior to the subsequent development of respiratory symptoms. Common and often very subtle symptoms included diarrhea, nausea, and abdominal pain, with a less common symptom being nonspecific GI illness.

New studies are expanding our understanding of the possible fecal transmission of COVID-19. Assessment by polymerase chain reaction (PCR) has provided evidence of virus in the stool and the oropharynx outside the nasopharynx and respiratory tract. Virus in the stool may be evident on presentation and last throughout the course of illness resolution for up to 12 days after the respiratory virus evidence is gone.

When I say "virus evidence," it's because it does not necessarily correspond to infectivity. Studies from fecal transmission to infectivity have yet to be done. However, it's certainly suggestive that the virus is intact, at least as far as how the PCR assay for the respiratory definition is now being applied the same way for stool.

Why Possible Fecal Transmission Is Important

The Centers for Disease Control and Prevention recommends that after two negative respiratory tests separated by ≥ 24 hours, patients can be dismissed from having transmissibility infection risk for COVID-19. But we now know that these stools may lag up to 12 days after. In fact, in one of the most recent studies looking at 73 patients, approximately 24% remained positive in their stool for evidence of virus, though not necessarily infection, after showing negative in respiratory samples.

When we consider other disease states with fecal-oral transmission, the classic example that comes to mind is Clostridium difficile. We tell patients with C difficile–positive stool that when they use and flush the toilet, they can aerosolize these spores, which may then deposit on the surface areas in their bathroom. As we do with C difficile, we may need to consider recommending the implementation of a high-level disinfection and mechanical disruption approach for COVID-19.

The latest science indicating that persistence may last up to 12 days after resolution of their respiratory infection or evidence of virus raises concerns around timing. How long should these patients be isolated from other people? Fecal-oral transmission has a real possibility for enhancing community spread, for active infected individuals and also for those less active infected and maybe those with concomitant illness that they just dismiss.

Another concern is the extrapulmonary manifestations of COVID-19. The most recent data suggest that transaminase elevation may be evident in some of these patients, at least those seen in Wuhan. This same hepatotoxicity was previously seen with SARS and MERS. It's not yet clear whether it's a direct viral effect on the liver or whether it's a concomitant effect from drugs (eg, antivirals, steroids, antibacterials) in patients who are sick or in the ICU. There's certainly more to be said on that topic.

Take Precautions

The potential for fecal-oral transmission of COVID-19 needs to be strongly considered. We need to start to look at some of those same isolation precautions we employ with C difficile. The potential for fecal transmissibility has yet to be defined, but we know from a recent study that the virus has been evident in the stool of just over 50% of patients and remains in nearly 25% otherwise clear of respiratory evidence of virus.

There's certainly more to be learned and understood. But at present, there's also a lot we may want to keep in mind as potential implications and precautions. I hope this provides you with good guidance.

I'm Dr David Johnson. Thanks again for listening.

David A. Johnson, MD, a regular contributor to Medscape, is professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia, and a past president of the American College of Gastroenterology. His primary focus is the clinical practice of gastroenterology. He has published extensively in the internal medicine/gastroenterology literature, with principal research interests in esophageal and colon disease, and more recently in sleep and microbiome effects on gastrointestinal health and disease.

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