COVID-19 is technically a respiratory infection so it came as a surprise when health authorities reported digestive issues as part of the symptomatology of the disease. Digestive issues such as a lack of appetite or poor appetite, nausea, vomiting, but also loose stools and diarrhea are some of the most common gastrointestinal symptoms of the novel Coronavirus infection. From data collected up to this point, it would appear that digestive symptoms, while unusual or atypical as some would say, may occur in up to half of all COVID-19 cases.
Why does the novel Coronavirus cause diarrhea, vomiting and other gastrointestinal symptoms? There are actually several potential explanations for GI symptoms in Coronavirus infections. For one, cells in the small and large intestine called enterocytes are susceptible to infection with SARS-CoV-2. This is because they have receptors on their surface such as ACE2 (angiotensin-converting enzyme 2) to which SARS-CoV-2 binds, resulting in subsequent infection. Then there is immune system involvement which triggers sometimes strong inflammatory responses that lead to destruction of infected cells which, in turn, affects digestive function and causes related gastrointestinal symptoms.
Digestive problems in novel Coronavirus infections may start out with symptoms not normally associated with respiratory infections. So aside from a sore throat, coughing, nasal congestion and fever, you may also be experiencing nausea, either mild or severe. While rather unusual for a respiratory infection as one may think, nausea is actually one of the earlier signs of a Coronavirus infection and can even precede more typical symptoms such as fever and shortness of breath, according to a report on the clinical characteristics of 138 hospitalized patients with 2019 novel Coronavirus infection.
But how is nausea a symptom of Coronavirus infection? The gastrointestinal tract is susceptible to infection with the novel Coronavirus, SARS-CoV-2. The cells that line the inside of the small and large intestine, called enterocytes or intestinal absorptive cells, have an enzyme on their surface known as angiotensin-converting enzyme 2, or ACE2. SARS-CoV-2 uses this enzyme to bind to the surface of intestinal cells and from there on infects them. It has been theorized that the subsequent involvement of the immune system response causes inflammation that can result in symptoms such as nausea. Enteric infections in general, including viral infections, are known to cause nausea. Its ability to infect cells in the small and large intestine makes the novel Coronavirus SARS-CoV-2 an enteric pathogen as well as a respiratory tract pathogen.
Of all the digestive symptoms of the novel Coronavirus infection, vomiting is one of the most debilitating, conducive to complications due to failure to eat and drink which predisposes to dehydration, weakness, weight loss and possibly also a longer recovery time or more difficult disease. Coronavirus-related vomiting is one of the less common, more unusual symptoms of COVID-19. From data collected up to this point, the incidence of vomiting and other digestive symptoms in Coronavirus infection may be as high as 50% in some groups, with vomiting occurring at low rates, or at least lower than most other digestive tract symptoms. In a study of 204 patients diagnosed with COVID-19, vomiting was observed to occur in almost 4% of cases.
(3) Poor appetite or lack of appetite
The novel Coronavirus infection can cause poor appetite or no appetite, depending on the case. COVID-19-related loss of appetite may seem like an atypical symptom, but is nonetheless fairly present in disease symptomatology. In a study of 204 patients diagnosed with COVID-19, lack of appetite was reported in almost 80% of cases (see last source). It is of less interest than other symptoms however due to its rather non-specific nature.
Loss of appetite in COVID-19 is theorized to be owed to direct infection of small and large intestine absorptive cells (enterocytes) with SARS-CoV-2 and also subsequent immune system involvement causing inflammation, leading to destruction of the cells and imbalances in digestive function. Though it may start out as poor appetite, the symptom may progress to complete lack of appetite. Coronavirus-related lack of appetite can be made worse by loss of smell and taste, both early symptoms of COVID-19.
Coronavirus diarrhea may be one of the more unusual symptoms of COVID-19 infection, but it’s reported to be the second most common digestive symptom after loss of appetite. In the same study of 204 patients diagnosed with COVID-19, diarrhea was reported in close to 35% of cases (source above). In some instances, it is also one of the earliest signs of a Coronavirus infection. In the same study of 138 hospitalized patients from Wuhan, China, infected with the 2019 novel Coronavirus, diarrhea and nausea occurred early on in the infection, earlier than typical respiratory symptoms such as fever and shortness of breath in roughly 10% of cases (source above).
How is diarrhea a symptom of Coronavirus infection? The novel Coronavirus, SARS-CoV-2, is known to infect cells in the small and large intestine known as enterocytes, in addition to lung cells, nervous system cells, heart muscle cells and blood vessels. By infecting intestinal cells and triggering immune system involvement and subsequent inflammation, the virus both destroys and disrupts normal cell activity causing malabsorption issues, imbalances in normal enzymatic secretion and motility disorders as a result of the activation of the enteric nervous system (the nervous system of the gastrointestinal tract). See source. This results in side effects that culminate with loose stools and diarrhea and associated digestive discomfort in the form of abdominal pain and cramps.
COVID-19 diarrhea causes systemic problems such as dehydration which may accentuate muscle weakness and even lead to a rise in blood pressure, albeit modest. Diarrhea is also an issue because it causes delays in seeking medical attention which raises the potential for developing severe forms of the disease and related complications.
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