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      COVID-19: Gastrointestinal Manifestations and Potential Fecal–Oral Transmission

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      Gastroenterology
      by the AGA Institute

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          Abstract

          The outbreak of novel coronavirus (2019-nCoV) pneumonia initially developed in one of the largest cities, Wuhan, Hubei province of China, in early December 2019 and has been declared the sixth public health emergency of international concern by the World Health Organization, and subsequently named coronavirus disease 2019 (COVID-19). As of February 20, 2020, a total of >75,000 cumulative confirmed cases and 2130 deaths have been documented globally in 26 countries across 5 continents. Current studies reveal that respiratory symptoms of COVID-19 such as fever, dry cough, and even dyspnea represent the most common manifestations at presentation similar to severe acute respiratory syndrome (SARS) in 2003 and Middle East respiratory syndrome in 2012, which is firmly indicative of droplet transmission and contact transmission. However, the incidence of less common features like diarrhea, nausea, vomiting, and abdominal discomfort varies significantly among different study populations, along with an early and mild onset frequently followed by typical respiratory symptoms. 1 Mounting evidence from former studies of SARS indicated that the gastrointestinal tract (intestine) tropism of SARS coronavirus (SARS-CoV) was verified by the viral detection in biopsy specimens and stool even in discharged patients, which may partially provide explanations for the gastrointestinal symptoms, potential recurrence, and transmission of SARS from persistently shedding human as well. 2 Notably, the first case of 2019-nCoV infection confirmed in the United States reported a 2-day history of nausea and vomiting on admission, and then passed a loose bowel movement on hospital day 2. The viral nucleic acids of loose stool and both respiratory specimens later tested positive. 3 In addition, 2019-nCoV sequence could be also detected in the self-collected saliva of most infected patients even not in nasopharyngeal aspirate, and serial saliva specimens monitoring showed declines of salivary viral load after hospitalization. 4 Given that extrapulmonary detection of viral RNA does not mean infectious virus is present, further positive viral culture suggests the possibility of salivary gland infection and possible transmission. 4 More recently, 2 independent laboratories from China declared that they have successfully isolated live 2019-nCoV from the stool of patients (unpublished). Taken together, a growing number of clinical evidence reminds us that digestive system other than respiratory system may serve as an alternative route of infection when people are in contact with infected wild animals or sufferers, and asymptomatic carriers or individuals with mild enteric symptoms at an early stage must have been neglected or underestimated in previous investigations. Clinicians should be careful to promptly identify the patients with initial gastrointestinal symptoms and explore the duration of infectivity with delayed viral conversion. To date, molecular modelling has revealed by the next-generation sequencing technology that 2019-nCoV shares about 79% sequence identify with SARS-CoV, indicative of these 2 lineage B β-coronaviruses highly homologous, and angiotensin-converting enzyme II (ACE2), previously known as an entry receptor for SARS-CoV, was exclusively confirmed in 2019-nCoV infection despite amino acid mutations at some key receptor-binding domains. 5 , 6 It is widely accepted that coronavirus human transmissibility and pathogenesis mainly depend on the interactions, including virus attachment, receptor recognition, protease cleaving and membrane fusion, of its transmembrane spike glycoprotein (S-protein) receptor-binding domain, specific cell receptors (ACE2), and host cellular transmembrane serine protease (TMPRSS), with binding affinity of 2019-nCoV about 73% of SARS-CoV. 7 Recent bioinformatics analysis on available single-cell transcriptomes data of normal human lung and gastrointestinal system was carried out to identify the ACE2-expressing cell composition and proportion, and revealed that ACE2 was not only highly expressed in the lung AT2 cells, but also in esophagus upper and stratified epithelial cells and absorptive enterocytes from ileum and colon. 8 With the increasing gastrointestinal wall permeability to foreign pathogens once virus infected, enteric symptoms like diarrhea will occur by the invaded enterocytes malabsorption, which in theory indicated the digestive system might be vulnerable to COVID-19 infection. In contrast, because ACE2 and TMPRSS especially TMPRSS2 are co-localized in the same host cells and the latter exerts hydrolytic effects responsible for S-protein priming and viral entry into target cells, further bioinformatics investigation renders additional evidence for enteric infectivity of COVID-19 in that the high co-expression ratio was found in absorptive enterocytes and upper epithelial cells of esophagus besides lung AT2 cells. However, the exact mechanism of COVID-19–induced gastrointestinal symptom largely remains elusive. Based on these considerations, ACE2-based strategies against COVID-19 such as ACE2 fusion proteins and TMPRSS2 inhibitors should be accelerated into clinical research and development for diagnosis, prophylaxis, or treatment. Last, mild to moderate liver injury, including elevated aminotransferases, hypoproteinemia, and prothrombin time prolongation, has been reported in the existing clinical investigations of COVID-19, whereas up to 60% of patients suffering from SARS had liver impairment. The presence of viral nucleic acids of SARS in liver tissue confirmed the coronavirus direct infection in liver, and percutaneous liver biopsies of SARS showed conspicuous mitoses and apoptosis along with atypical features such as acidophilic bodies, ballooning of hepatocytes, and lobular activities without fibrin deposition or fibrosis. 9 It is believed that SARS-associated hepatotoxicity may be likely with viral hepatitis or a secondary effect associated with drug toxicity owing to high-dose consumption of antiviral medications, antibiotics, and steroids, as well as immune system overreaction. However, little is known about 2019-nCoV infection in liver. Surprisingly, recent single cell RNA sequencing data from 2 independent cohorts revealed a significant enrichment of ACE2 expression in cholangiocytes (59.7% of cells) instead of hepatocytes (2.6% of cells), suggesting that 2019-nCoV might lead to direct damage to the intrahepatic bile ducts. 10 Altogether, substantial effort should be made to be alert on the initial digestive symptoms of COVID-19 for early detection, early diagnosis, early isolation, and early intervention.

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          Most cited references7

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          Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus–Infected Pneumonia in Wuhan, China

          In December 2019, novel coronavirus (2019-nCoV)-infected pneumonia (NCIP) occurred in Wuhan, China. The number of cases has increased rapidly but information on the clinical characteristics of affected patients is limited.
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            Is Open Access

            A pneumonia outbreak associated with a new coronavirus of probable bat origin

            Since the outbreak of severe acute respiratory syndrome (SARS) 18 years ago, a large number of SARS-related coronaviruses (SARSr-CoVs) have been discovered in their natural reservoir host, bats 1–4 . Previous studies have shown that some bat SARSr-CoVs have the potential to infect humans 5–7 . Here we report the identification and characterization of a new coronavirus (2019-nCoV), which caused an epidemic of acute respiratory syndrome in humans in Wuhan, China. The epidemic, which started on 12 December 2019, had caused 2,794 laboratory-confirmed infections including 80 deaths by 26 January 2020. Full-length genome sequences were obtained from five patients at an early stage of the outbreak. The sequences are almost identical and share 79.6% sequence identity to SARS-CoV. Furthermore, we show that 2019-nCoV is 96% identical at the whole-genome level to a bat coronavirus. Pairwise protein sequence analysis of seven conserved non-structural proteins domains show that this virus belongs to the species of SARSr-CoV. In addition, 2019-nCoV virus isolated from the bronchoalveolar lavage fluid of a critically ill patient could be neutralized by sera from several patients. Notably, we confirmed that 2019-nCoV uses the same cell entry receptor—angiotensin converting enzyme II (ACE2)—as SARS-CoV.
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              Genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding

              Summary Background In late December, 2019, patients presenting with viral pneumonia due to an unidentified microbial agent were reported in Wuhan, China. A novel coronavirus was subsequently identified as the causative pathogen, provisionally named 2019 novel coronavirus (2019-nCoV). As of Jan 26, 2020, more than 2000 cases of 2019-nCoV infection have been confirmed, most of which involved people living in or visiting Wuhan, and human-to-human transmission has been confirmed. Methods We did next-generation sequencing of samples from bronchoalveolar lavage fluid and cultured isolates from nine inpatients, eight of whom had visited the Huanan seafood market in Wuhan. Complete and partial 2019-nCoV genome sequences were obtained from these individuals. Viral contigs were connected using Sanger sequencing to obtain the full-length genomes, with the terminal regions determined by rapid amplification of cDNA ends. Phylogenetic analysis of these 2019-nCoV genomes and those of other coronaviruses was used to determine the evolutionary history of the virus and help infer its likely origin. Homology modelling was done to explore the likely receptor-binding properties of the virus. Findings The ten genome sequences of 2019-nCoV obtained from the nine patients were extremely similar, exhibiting more than 99·98% sequence identity. Notably, 2019-nCoV was closely related (with 88% identity) to two bat-derived severe acute respiratory syndrome (SARS)-like coronaviruses, bat-SL-CoVZC45 and bat-SL-CoVZXC21, collected in 2018 in Zhoushan, eastern China, but were more distant from SARS-CoV (about 79%) and MERS-CoV (about 50%). Phylogenetic analysis revealed that 2019-nCoV fell within the subgenus Sarbecovirus of the genus Betacoronavirus, with a relatively long branch length to its closest relatives bat-SL-CoVZC45 and bat-SL-CoVZXC21, and was genetically distinct from SARS-CoV. Notably, homology modelling revealed that 2019-nCoV had a similar receptor-binding domain structure to that of SARS-CoV, despite amino acid variation at some key residues. Interpretation 2019-nCoV is sufficiently divergent from SARS-CoV to be considered a new human-infecting betacoronavirus. Although our phylogenetic analysis suggests that bats might be the original host of this virus, an animal sold at the seafood market in Wuhan might represent an intermediate host facilitating the emergence of the virus in humans. Importantly, structural analysis suggests that 2019-nCoV might be able to bind to the angiotensin-converting enzyme 2 receptor in humans. The future evolution, adaptation, and spread of this virus warrant urgent investigation. Funding National Key Research and Development Program of China, National Major Project for Control and Prevention of Infectious Disease in China, Chinese Academy of Sciences, Shandong First Medical University.
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                Author and article information

                Journal
                Gastroenterology
                Gastroenterology
                Gastroenterology
                by the AGA Institute
                0016-5085
                1528-0012
                3 March 2020
                3 March 2020
                Affiliations
                [1]Shanghai Jiao Tong University School of Medicine, Shanghai, China
                Article
                S0016-5085(20)30281-X
                10.1053/j.gastro.2020.02.054
                7130192
                32142785
                cf090618-9f38-4bd9-91e2-5404f7d4c801
                © 2020 by the AGA Institute.

                Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

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                Gastroenterology & Hepatology
                Gastroenterology & Hepatology

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