COVID-19 infection, caused by the SARS-CoV-2 virus, is widely recognized for its impact on the respiratory system, leading to symptoms like cough and fever. However, the disease is not strictly confined to the lungs, and a significant number of patients experience symptoms affecting the digestive tract. Gastrointestinal (GI) involvement, including nausea and vomiting, is a common feature of the infection that often surprises those who associate the illness primarily with respiratory distress. Understanding this broader symptom profile is important for accurate diagnosis and effective management of the illness.
Nausea and Vomiting as Recognized Symptoms
Nausea and vomiting are established symptoms of COVID-19. Their frequency can vary widely depending on the study population, ranging from about 1% to nearly 30% in adults diagnosed with the infection. Nausea is reported more frequently than vomiting, with a median incidence around 10.5% in analyzed patient populations. While fever and cough are often considered the hallmark signs, GI issues like nausea, vomiting, and diarrhea are present in a notable subset of cases.
For some individuals, these digestive symptoms can appear very early in the illness, sometimes even before the onset of more typical respiratory signs. This early presentation can complicate diagnosis, as patients may initially assume they have a common stomach bug. Although less common, some people may experience GI symptoms, including vomiting, with no accompanying respiratory symptoms at all.
The presence of nausea and vomiting, along with other GI symptoms, is an important indicator of infection that should not be overlooked. They can be a substantial part of the acute infection phase and, in some cases, may persist for weeks or months as part of long COVID. Recognizing these digestive complaints as a potential sign of COVID-19 is necessary for early isolation and testing.
The Biological Reason for Gastrointestinal Symptoms
The SARS-CoV-2 virus gains entry into human cells by binding to the Angiotensin-Converting Enzyme 2 (ACE2) receptor. While this receptor is abundant in the lungs, it is also highly expressed in the epithelial cells lining the digestive tract, particularly in the small intestine. Research suggests that ACE2 expression in the GI tract can be significantly higher than in airway epithelial cells.
The presence of ACE2 receptors in the stomach, duodenum, and rectum allows the virus to directly invade and replicate within the cells of the gut lining. This direct viral infection causes damage to the intestinal mucosal barrier, leading to inflammation and disruption of normal gut function. The resulting irritation and inflammation of the stomach and intestinal tissues contribute to the feelings of nausea and vomiting.
Beyond direct cell invasion, the binding of the virus to the ACE2 receptor can lead to a deficiency in ACE2 activity. ACE2 plays a role in regulating intestinal inflammation, and its dysregulation is thought to contribute to the overall GI distress observed in COVID-19 patients. Furthermore, the infection can disturb the balance of the gut microbiome, the community of bacteria and other microbes in the digestive system. This shift in microbial balance, known as dysbiosis, can also intensify the inflammation and GI symptoms.
Managing Nausea, Vomiting, and Dehydration
The primary concern when dealing with vomiting and nausea is the risk of dehydration, which can quickly worsen the overall feeling of illness. It is important to focus on replacing lost fluids and electrolytes, even if only small amounts can be tolerated at a time. Rather than attempting to drink large glasses of water, patients should sip clear fluids frequently, such as broth, diluted fruit juice, or oral rehydration solutions.
Electrolyte solutions are particularly useful because they contain the necessary balance of salts and sugars to help the body absorb water efficiently. When the nausea subsides, a patient can gradually introduce bland, easy-to-digest foods. The BRAT diet—bananas, rice, applesauce, and toast—is often recommended, as these foods are gentle on the stomach and less likely to trigger a return of symptoms.
It is helpful to eat smaller, more frequent snack-sized meals instead of three large meals, as an overly full stomach can aggravate nausea. Strong food odors can also be a trigger, so eating cold or room-temperature foods may be easier to manage than hot meals. Certain symptoms, often referred to as “red flags,” indicate the need to seek immediate medical attention.
Patients should contact a healthcare provider if they experience any of the following:
- Inability to keep any fluids down for 24 hours.
- Vomiting three or more times in a single day.
- Inability to urinate for eight hours or more, which signals severe dehydration.
- Severe abdominal pain.
- Signs of extreme weakness, confusion, or difficulty breathing alongside GI symptoms.