By David Wild

Researchers in China are warning that the virus causing the novel coronavirus infection COVID-19, which has affected over 100,000 people and killed more than 3,200 globally, can potentially be transmitted through feces.

The reports, published online in Gastroenterology, found that more than 50% of people infected with SARS-CoV-2 have the virus in their stool; some patients have vomiting and diarrhea; and some test positive for virus in stool even after respiratory samples test negative for the pathogen.

“A better understanding of how this virus is transmitted is key to preventing its spread,” said Douglas Corley, MD, PhD, the director of delivery science and applied research and a gastroenterologist and research scientist at Kaiser Permanente, Northern California, and the co-editor of Gastroenterology. Dr. Corley was not involved in the research.

“These observations may help improve how the disease is more efficiently diagnosed through testing for the presence of virus in the stool of patients suspected of harboring this virus.”

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In one study (Gastroenterology 2020; doi: https://doi.org/10.1053/j.gastro.2020.02.055), Fei Xiao, MD, PhD, of the Fifth Affiliated Hospital in Guangzhou, China, and colleagues followed up on a previous finding of SARS-CoV-2 RNA in a patient’s stool.

Dr. Xiao’s team conducted polymerase chain reaction (PCR) testing in 71 patients hospitalized at their institution for COVID-19 during Feb. 1-14, 2020. They also studied esophageal, gastric, duodenal and rectal biopsies taken from one of the patients who also underwent endoscopy.

The researchers found that 53.4% of patients had SARS-CoV-2 RNA in their stool and 23% of patients tested positive in their stool despite testing negative for the virus in respiratory samples.

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This finding indicates that “viral gastrointestinal infection and the potential fecal–oral transmission can last even after viral clearance in [the] respiratory tract,” they reported.

“Therefore, we strongly recommend that rRT [real-time reverse transcription]-PCR testing for SARS-CoV-2 from feces should be performed routinely in SARS-CoV-2 patients, and Transmission-Based Precautions for hospitalized SARS-CoV-2 patients should continue if feces tests positive by rRT-PCR testing.”

In the patient who underwent endoscopy, the investigators found numerous infiltrating plasma cells and lymphocytes as well as interstitial edema in the lamina propria of the stomach, duodenum and rectum.

In a separate publication (Gastroenterology 2020; https://doi.org/10.1053/j.gastro.2020.02.054), Jinyang Gu, MD, of the Department of Transplantation at Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine in Shanghai, China, and colleagues noted that during the 2003 outbreak of severe acute respiratory syndrome (SARS), “viral detection in [gastrointestinal] biopsy specimens and stool even in discharged patients … partially provide[d] explanations for the gastrointestinal symptoms, potential recurrence and transmission of SARS from persistently shedding human[s].”

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The first patient in the United States diagnosed with SARS-CoV-2 infection reported two days of nausea and vomiting before presenting to the hospital, and had loose bowel movements while in the hospital. Both stool and respiratory specimens from the patient tested positive for SARS-CoV-2, the authors said.

The small but growing body of clinical evidence indicates the digestive system may serve as an alternative route of SARS-CoV-2 infection in addition to the respiratory tract, they stressed, adding that “clinicians should be careful to promptly identify the patients with initial gastrointestinal symptoms.”

Some patients with COVID-19 have also experienced mild to moderate liver injury, Dr. Gu’s team noted. Although how the new virus affects the liver is unclear, during the 2003 SARS outbreak, liver tissue biopsies confirmed direct hepatic infection. Recent data from two independent cohorts also suggest SARS-CoV-2 infection can directly damage intrahepatic bile ducts, the authors said.

“Altogether, [data to date suggest that] many efforts should be made to be alert [for] the initial digestive symptoms of COVID-19 for early detection, early diagnosis, early isolation and early intervention,” they wrote.