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MARCH 11, 2020 -- Fecal-oral transmission may be part of the COVID-19 clinical picture, according to two reports published in Gastroenterology. The researchers find that RNA and proteins from SARS-CoV-2, the viral cause of COVID-19, are shed in feces early in infection and persist after respiratory symptoms abate.
But the discovery is preliminary. "There is evidence of the virus in stool, but not evidence of infectious virus," David A. Johnson, MD, professor of medicine and chief of gastroenterology at the Eastern Virginia School of Medicine in Norfolk, told Medscape Medical News.
The findings are not entirely unexpected. Both of the coronaviruses behind SARS and MERS are shed in stool, Jinyang Gu, MD, from Shanghai Jiao Tong University School of Medicine in Shanghai, China, and colleagues, note in one of the newly published articles.
In addition, as COVID-19 spread beyond China, clinicians began noticing initial mild gastrointestinal (GI) symptoms in some patients, including diarrhea, nausea, vomiting, and abdominal pain, preceding the hallmark fever, dry cough, and dyspnea. The first patient diagnosed in the United States with COVID-19 reported having 2 days of nausea and vomiting, with viral RNA detected in fecal and respiratory specimens, according to an earlier report.
Gu and colleagues warn that initial investigations would likely have not considered cases that manifested initially only as mild gastrointestinal symptoms.
Although early reports indicated that only about 10% of people with COVID-19 have GI symptoms, it isn't known whether some infected individuals have only GI symptoms, Johnson said.
The GI manifestations are consistent with the distribution of ACE2 receptors, which serve as entry points for SARS-CoV-2, as well as SARS-CoV-1, which causes SARS. The receptors are most abundant in the cell membranes of lung AT2 cells, as well as in enterocytes in the ileum and colon.
"Altogether, many efforts should be made to be alert on the initial digestive symptoms of COVID-19 for early detection, early diagnosis, early isolation and early intervention," Gu and colleagues conclude.
But Johnson cautions, "gastroenterologists are not the ones managing diagnosis of COVID-19. It is diagnosed as a respiratory illness, but we are seeing concomitant gastrointestinal shedding in stool and saliva, and GI symptoms."
Samples From 73 Patients Studied
In the second article published, Fei Xiao, MD, of Sun Yat-sen University in Guangdong Province, China, and colleagues report detecting viral RNA in samples from the mouths, noses, throats, urine, and feces of 73 patients hospitalized during the first 2 weeks of February.
Of the 73 hospitalized patients, 39 (53.24%; 25 males and 14 females) had viral RNA in their feces, present from 1 to 12 days. Seventeen (23.29%) of the patients continued to have viral RNA in their stool after respiratory symptoms had improved.
One patient underwent endoscopy. There was no evidence of damage to the GI epithelium, but the clinicians detected slightly elevated levels of lymphocytes and plasma cells.
The researcher used laser scanning confocal microscopy to analyze samples taken during the endoscopy. They found evidence of both ACE2 receptors and viral nucleocapsid proteins in the gastric, duodenal, and rectal glandular epithelial cells.
Finding evidence of SARS-CoV-2 throughout the GI system, if not direct infectivity, suggests a fecal-oral route of transmission, the researchers conclude. "Our immunofluorescent data showed that ACE2 protein, a cell receptor for SARS-CoV-2, is abundantly expressed in the glandular cells of gastric, duodenal and rectal epithelia, supporting the entry of SARS-CoV-2 into the host cells."
Detection of viral RNA at different time points in infection, they write, suggests that the virions are continually secreted and therefore likely infectious, which is under investigation. "Prevention of fecal-oral transmission should be taken into consideration to control the spread of the virus," they write.
Current recommendations do not require that patients' fecal samples be tested before being considered noninfectious. However, given their findings and evidence from other studies, Xiao and colleagues recommend that real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) testing of fecal samples be added to current protocols.
Johnson offers practical suggestions based on the "potty hygiene" suggestions he gives to patients dealing with fecal shedding in Clostridioides difficile infection.
"To combat the microaerosolization of C. diff spores, I have patients do a complete bacteriocidal washing out of the toilet bowl, as well as clean surface areas and especially toothbrushes." Keeping the bowl closed when not in use is important too in preventing "fecal-oral transmission of remnants" of toilet contents, he adds.
The new papers add to other reports suggesting that virus-bearing droplets may reach people in various ways, Johnson said. "Maybe the virus isn't only spread by a cough or a sneeze."
The researchers and commentator have disclosed no relevant financial relationships.
Gastroenterology. 2020. doi: https://doi.org/10.1053/ j.gastro.2020.02.054.