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How does COVID-19 get into GI tract?

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How does COVID-19 get into GI tract?

When it penetrates the gut lining, it can spread to the gut-lung axis, and most severe cases that we’re seeing are related to gut involvement...

How does COVID-19 get into GI tract?

Specialist’s Corner

Dr  Deepak K Agarwal

The writer is senior consultant  gastroenterologist, hepatologist & endoscopist and is running a successful medical Centre in Lucknow

COVID-19 frequently affects the GI system because SARS-CoV-2, the virus that causes the disease, enters the system through a protein called ACE-2, according to a study published in September 2021 in Frontiers in Molecular Biosciences. ACE-2 is vital to regulating blood pressure and nutrient absorption and is found in several organs, including the heart, kidney, and lungs, as well as the small intestine and the colon. A study published in the American Journal of Gastroenterology in January 2022 found that nearly 60 percent of hospitalized COVID-19 patients complained of GI symptoms.

When it penetrates the gut lining, it can spread to the gut-lung axis, and most severe cases that we’re seeing are related to gut involvement. We’ve seen an uptick in sepsis from bacteria due to COVID. When the gut lining becomes leaky or permeable, we see bacteria leaking into the body, getting into the system, and that causes problems. I did not know of any particular population that was more susceptible to COVID-related GI symptoms, but there was a debate within the professional community about whether there should be increased concern for patients who do not have acid in their GI system. Otherwise, research has focused on the gut microbiome’s role in tamping down inflammation that runs from the gut to the lungs. New research suggests there is an axis of communication where intestinal microbial communities have a profound effect on lung disease, according to an analysis in the February 2020 Frontiers in Cellular and Infection Microbiology.

An October 2021 review in Frontiers in Immunology looked into the possibility that targeted therapy for the gut microbiome can prevent the leaky gut phenomenon that allows bacteria to permeate the lining of the intestine and enter the circulatory system. The health of the gut microbiome — variety and quantity — has emerged in research as an indicator of better COVID-19 outcomes. Both a study published in March 2021 in Gut and a study published in January 2022 in BMC Medicine compared the gut flora of people infected with COVID-19 and people who weren’t. Those who were not infected or had better outcomes had more gut flora, a higher concentration of microbes that boosted immunity, and greater bacterial diversity in their gut. Those who fared worse or were more susceptible to “long COVID” had a less-diverse microbiome and a greater concentration of harmful bacteria. A study published in Gut in January 2022 found that people who suffered from long COVID had their gut microbiome altered by the disease for over six months after COVID-19 left their system. Patients who had lingering respiratory symptoms showed increased levels of a bacterium known to attack the gut-lung axis, while people with depression or fatigue had greater concentrations of gut bacteria associated with those conditions.

The gut houses the largest organ of the immune system, so it is no surprise that the health of the microbiome will influence the immune response to SARS-CoV-2. The good news is that experts are much less worried about COVID-19 than they were at the beginning of the pandemic; data at the time showed that the initial symptoms of patients with digestive issues worsened as the virus grew stronger. It could be the increased immunity from vaccines coupled with the changes in the virus, but we are not seeing the severe manifestations and catastrophic outcomes that we first saw. We are not seeing overwhelming sepsis as frequently as we did at the beginning of the pandemic. While the severity of GI symptoms has diminished, there has been a nationwide uptick in irritable bowel syndrome (IBS) cases. We are seeing cases where people are left with IBS long after COVID seems to have disappeared. And while we are seeing an increase in prevalence across the population, we do not have the data to say it is from COVID. It could be stress, or something we have not pinpointed yet.

While the frequency of severe GI complications has declined, a paper published in the Lancet Gastroenterology and Hepatology in May 2021 noted that severe cases of COVID-19 often lead to severe GI complications, including acute liver injury, elevated enzyme levels, acute pancreatitis, and an inability to eat. The review also highlighted some long-term effects, including loss of appetite, frequent bouts of diarrhea, or persistent nausea. In a small subset of patients, a COVID infection can lead to the development of irritable bowel syndrome. This would be called a post infection IBS state. We also now recognize that COVID can affect the liver and lead to liver test abnormalities and, rarely, more serious complications. People must remain cautious even though the majority of cases have mild symptoms. This time people are coming up with diarrhoea but symptoms are milder now. Very less hospitalisation has been seen. The people who come under Comorbidities are reporting hospitalization. Earlier several studies have pointed out that Omicron BA.2 patients often complain of six gut-related sicknesses -nausea, diarrhoea, vomiting, abdominal pain, heartburn, bloating. Physicians are just learning how different virus variants can affect the GI tract. More data will be coming out in the next few years.

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