Stomach flu is actually viral gastroenteritis

DEAR DOCTORS: Our family just spent two weeks passing around a nasty stomach flu. Now that we’re all OK, I realise I don’t know what hit us. Was it the same bug that gives you the regular flu? How does it get from one person to another?

DEAR READER: What we commonly refer to as “stomach flu” is more accurately known as “viral gastroenteritis”. It’s different from the actual flu, which is a respiratory illness that affects the throat, nose and lungs. Unlike the flu, which is caused by the influenza virus, stomach flu typically arises from infection with a different set of viruses. They target the gastrointestinal tract, which includes the stomach and the large and small intestines.

The two most common causes of viral gastroenteritis are rotaviruses and noroviruses. Rotavirus disease is most often seen in infants and young children. Older children and adults can also become infected, but their symptoms tend to be less severe. Noroviruses, which are the most common cause of stomach flu in adults, can affect children as well.

Both rotaviruses and noroviruses are highly contagious. They spread through direct contact with contaminated food, drink, dishes, utensils and surfaces, and through close contact with an infected individual. Both of the viruses are shed in a contaminated person’s stool. If that person fails to thoroughly wash their hands after a bowel movement, they can spread the live virus to everything that they touch.

Symptoms of viral gastroenteritis typically begin 12 to 48 hours after infection. They include stomach discomfort or cramping, feeling nauseated, vomiting, persistent diarrhoea, loss of appetite and exhaustion. Some people also have muscle aches, headache or a low-grade fever. Diagnosis is based on someone’s symptoms, plus a physical exam. A stool sample may be used to rule out bacterial or parasitic illness, which can have similar symptoms. A mild case of viral gastroenteritis lasts for two to three days. A more severe infection can persist for a week or more.

One of the risks of this type of illness is becoming dehydrated. This is due to the fluids lost through diarrhoea and vomiting, which can be difficult to replace when you’re feeling too nauseated to eat or drink. This is particularly dangerous for the very young and for older adults. It’s important for someone with gastroenteritis to stay hydrated by drinking small amounts of clear fluids throughout the day. Drinking too much, or too quickly, can increase nausea. Younger and older patients may require special oral rehydration fluids.

You should seek guidance on these from your healthcare provider. It’s important to be alert to signs of dehydration. These include dry skin, dry mouth, little or no urine, urine that is a deep yellow colour, or feeling faint, dizzy or lightheaded. If these occur, seek medical help immediately.

Since antibiotics don’t work against viruses, treatment focuses on easing the patient’s symptoms. This includes rest, hydration and a bland diet as you gradually ease back into eating. New parents might consider asking their paediatrician about the rotavirus vaccine, which is effective at preventing serious symptoms.

Dr Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health.