The current outbreak of the novel coronavirus, SARS-CoV-2 (coronavirus disease 2019; previously 2019- nCoV), epi-centered in Hubei Province of the People's Republic of China, has spread to many other countries caused an extreme burden for healthcare systems globally. Coronaviruses are traditionally considered nonlethal pathogens to humans, mainly causing approximately 15% of common colds. In this century, we have encountered highly pathogenic human CoVs twice. In this chapter, the authors propose to focus the gastrointestinal physiopathology of the infection of SARS-Cov2. This chapter will develop subject like the gastrointestinal manifestations of the infection to SARS-Cov2. The second part of this chapter will develop the role of the gut microbiome in the SARS-Cov2 diseases susceptibilities. And then the authors will show the etiopathogenesis of SARS-Cov2 associated diarrhea. As reported by previous studies, the SARS-Cov virus entry into host cell is mediated by the interaction between the envelop-anchored viral spike protein and the host receptor named angiotensin-converting enzyme 2 (ACE2).
TopIntroduction
The current outbreak of the novel Coronavirus, Severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) (Coronavirus disease 2019; previously 2019-nCoV), epi-centered in Hubei Province of the People’s Republic of China, has spread to many other countries and caused an extreme burden for health care systems globally. Coronavirus have been traditionally considered as non-lethal pathogens to humans, mainly causing approximately 15% of common colds. However, in this century, we have encountered highly pathogenic human CoVs twice, i.e., SARS-CoV and Middle East respiratory syndrome Coronavirus (MERS-CoV), which caused outbreaks respectively in China in 2003 and Saudi Arabia in 2012 (Assiri et al., 2013; Hoffmann et al., 2020a).
Although this viral infection is mainly manifested with fever, dry cough and shortness of breath, respiratory symptom and inflammation. Symptoms like Gastrointestinal manifestations have been reported to be associated to the infection to SARS-Cov2 (Del Rio and Malani, 2020). This virus uses the Angiotensin-Converting Enzyme 2 (ACE2) receptor in order to invade cells, and these receptors have been reported to be highly expressed in both respiratory and gastrointestinal tracts (Xiao et al., 2020; Wang et al., 2020),suggesting that the digestive tract might be an extra-pulmonary site for virus replication and activity (Wolfel et al., 2020; Xu et al., 2020).Accumulating evidence in these days suggest that, this coronavirus, may also be considered as an enteric virus, which can be spread via the fecal-oral route (Guan et al., 2020; Holshue et al., 2020). The most commonly reported Gastrointestinal(GI) manifestation of Covid-19are diarrhea, abdominal pain, nausea or vomiting, which are reported in a third to up even more than half of the patients (Parasa et al., 2020).
The gut microbiota demonstrates tremendous diversity and variation of commensal bacterial populations, and this explains how the gut microbiota plays a vital role in the outcome of diseases. Several studies have confirmed that gut microbiota plays a key role in health through the immunity building mechanism (Chung et al., 2012; Bouskra et al., 2008; Mazmanian et al., 2005). This commensal microbiota in the gut tract ecosystem is dynamic and can be regulated by invading viruses to facilitate a stimulatory or suppressive response (Ma et al., 2019). Mounting evidences have supported the hypothesis that, the composition of the gut microbiome could partially explain the difference in susceptibility of Covid-19 patients. There are few cues that support this possibility of the gut microbiota link to Covid-19. The first one is the presence of many SARS-Cov2 viral RNA in the faeces of many patients. Secondly, the various gastrointestinal symptoms reported by patients. Thirdly, the fact that most vulnerable patients were the old people, immune-compromised and patients with co-morbidities And the fourth one is the greater evidences of the Gut-lung axis. Where it is emphasized the role played by gut microbiome diversity and abundance in SARS-Cov2 susceptibility (Busra and Belma, 2020). In all such people, studies have revealed a gut dysbiosis and decreased gut diversity.