COVID-19 pandemic: Pathophysiology and manifestations from the gastrointestinal tract

Abstract

The pandemic of coronavirus disease 2019 (COVID-19), caused by a newly identified β-coronavirus (SARS-CoV-2) has emerged as a dire health problem, causing a massive crisis for global health. Primary method of transmission was firstly thought to be animal to human transmission. However, it has been observed that the virus is transmitted from human to human via respiratory droplets. Interestingly, SARS-CoV-2 ribonucleic acid (RNA) has been isolated from patient stools, suggesting a possible gastrointestinal (GI) involvement. Most commonly reported clinical manifestations are fever, fatigue and dry cough. Interestingly, a small percentage of patients experience GI symptoms with the most common being anorexia, diarrhea, nausea and vomiting. The presence of viral RNA in stools is also common and fecal tests can be positive even after negative respiratory samples. The exact incidence of digestive symptoms is a matter of debate. The distribution of Angiotensin converting enzyme type 2 receptors in multiple organs in the body provides a possible explanation for the digestive symptoms' mechanism. Cases with solely GI symptoms have been reported in both adults and children. Viral RNA has also been detected in stool and blood samples, indicating the possibility of liver damage, which has been reported in COVID-19 patients. The presence of chronic liver disease appears to be a risk factor for severe complications and a poorer prognosis, however data from these cases is lacking. The aim of this review is firstly, to briefly update what is known about the origin and the transmission of SARS-CoV-2, but mainly to focus on the manifestations of the GI tract and their pathophysiological background, so that physicians on the one hand, not to underestimate or disregard digestive symptoms due to the small number of patients exhibiting exclusively this symptomatology and on the other, to have SARS-CoV-2 on their mind when the "gastroenteritis" type symptoms predominate.

Keywords: ACE2 receptors and COVID-19; COVID-19; COVID-19 and gastrointestinal pathophysiology; COVID-19 gastrointestinal manifestations; COVID-19 on chronic liver diseases; Gastrointestinal tract; SARS-CoV-2.

Figure 1

Phylogenetic relationship of the various types of coronaviruses within the family Coronaviridae, subfamily Orthocoronavirinae and their respective genera: Alpha, beta, gamma, and deltacoronavirus. Coronaviridae is the largest family within the order of Nidovirales. Family Coronaviridae includes subfamily Torovirinae and subfamily Orthocoronavirinae. Subfamily Orthocoronavirinae comprises four genera: Alphacoronavirus, betacoronavirus, gammacoronavirus and deltacoronavirus. Genomic characterization has shown that probably rodents and bats ate the gene sources of alphacoronavirus and betacoronavirus. The above diagram was created with Biorender.com. SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2; MERS-CoV: Middle East respiratory syndrome coronavirus; SARS-CoV: Severe acute respiratory syndrome coronavirus.

Figure 2

Transmission cycle of severe acute respiratory syndrome coronavirus 2. The above diagram was created with http://www.Biorender.com. SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2; ACE2: Angiotensin converting enzyme type 2.