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All About Acute Gastroenteritis Symptoms in Adults

Written by Stephanie Nera, RPh, PharmD · Pharmacology

Updated Jul 06, 2021

All About Acute Gastroenteritis Symptoms in Adults

Acute gastroenteritis can be caused by either viruses or bacteria. Rotavirus and norovirus are the most common causes of viral gastroenteritis. Fortunately, acute gastroenteritis symptoms in adults are typically mild. They are somewhat generic and can easily be mistaken for other illnesses. Viral infections are self-limiting and doctors can treat only the symptoms. On the other hand, bacterial infections need to be treated with antibiotics to cure the illness. Below are the typical symptoms of both viral and bacterial acute gastroenteritis in adults.

Acute gastroenteritis symptoms in adults


Diarrhea is one of the most common symptoms of acute gastritis in both adults and children. It can be defined as the passage of loose or watery stools (as compared to your usual bowel movements). Acute episodes of diarrhea lasts between 1 and 14 days. Longer than this is considered persistent or chronic.

While it usually goes away after a few days, severe diarrhea can lead to dehydration and electrolyte imbalances. These can cause weakness, changes in mood and mental state, and even loss of consciousness. 

In addition, it is important to remember that gastroenteritis is contagious. It often spreads person to person through unwashed hands and contaminated food. To avoid spreading or getting infected, always practice proper handwashing and thoroughly cook your food.

Acute Gastroenteritis Symptoms in Adults

Abdominal cramps

Abdominal cramping can range from mild to severe. This kind of cramping is due to the changes in bowel or intestinal movement. Bacteria in the gut, both the normal flora and any pathogenic bacteria, can produce toxins and gases. As these bacteria multiply and feed on food matter in the gut, they release gases as a byproduct of metabolism.

This gas can build up in the intestinal tract and cause bloating, flatulence, abdominal cramping, and discomfort. Taking medications to reduce gassiness can help relieve these symptoms. Passing gas and belching is another way to remove excess gas from the bowels.


Nausea is a feeling of discomfort with the need to vomit, though it can occur without vomiting. It is a very common symptom of many diseases and is therefore not specific to acute gastroenteritis in adults. 

It can occur even without disease, as there are a lot of medications that can cause nausea and vomiting. Nausea in gastroenteritis may be due to the release of toxins from the bacteria or a delay in stomach emptying after meals (gastroparesis). 

Damaged cells and immune cells release chemicals which trigger a response in the brain. The amount of chemical signals that reach the brain determines the severity of nausea and vomiting. 


Fever is another common symptom of many illnesses. The presence of a fever almost always indicates there is an infection. While a fever may not always be present with acute gastroenteritis, it can be an indicator for a more serious infection.

Fevers occur as a natural defense mechanism against bacteria and viruses. The body heats itself up in an attempt to kill the pathogens. Low-grade fevers are above 38°C, while high-grade fevers are 39.4°C or higher. Prolonged high-grade fevers can cause more harm than good. High-grade fevers above 40°C for several hours to days can even cause permanent brain and nerve damage.

Dehydration-related symptoms

Dehydration is a concern whenever there is fluid leaving the body, especially with diarrhea and vomiting. Frequent, watery stools can cause the loss of not only water but also essential nutrients, vitamins, and electrolytes.

Dehydration itself is not a symptom, but rather its own condition. Because people lose more than just water during episodes of diarrhea, it is important to rehydrate with both water and electrolytes. 

Mild signs of dehydration include dry or chapped lips and feelings of extreme thirst. Severe signs and symptoms of dehydration include muscle weakness and loss of consciousness. Mild dehydration can be treated at home while more severe dehydration is a medical emergency.

Acute Gastroenteritis Symptoms in Adults


Tenesmus is the medical term that refers to rectal discomfort with a sense of needing to pass a stool, even if you recently emptied your bowels. In an effort to make a bowel movement, you may bear down or strain excessively which can make things worse. Excessive or prolonged straining can cause a drop in blood pressure, which may cause lightheadedness or fainting.

Tenesmus is also a symptom of inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis. However, tenesmus alone is not enough to diagnose IBD or gastroenteritis.

Other conditions with similar symptoms

Key takeaways

To summarize, acute gastroenteritis symptoms in adults are generally mild and fairly easy to treat. Early treatment and frequent monitoring is important to prevent severe symptoms like dehydration and discomfort.

Aside from adequate hydration, bed rest, and medication, hand washing is the best way to prevent spreading gastroenteritis to others. Lastly, if you are experiencing any of these symptoms, consult your doctor.

Learn more about Digestive Health here.


Hello Health Group does not provide medical advice, diagnosis or treatment.

Written by

Stephanie Nera, RPh, PharmD


Updated Jul 06, 2021

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