Is stomach flu a real thing?

Though commonly mistaken for influenza (the flu), the stomach flu is not really the flu at all.

Influenza affects only the respiratory system — the nose, throat, and lungs — and is caused by the influenza virus. The flu is highly contagious and comes on suddenly. Primary symptoms include fever (100 to 103 degrees Fahrenheit in adults and often higher in children), cough, sore throat, muscle or body aches, headaches, and fatigue. Most people completely recover from the flu in one to two weeks, according to the Illinois Department of Public Health.

Stomach flu is sometimes used to describe gastrointestinal illnesses caused by organisms (usually viruses) other than influenza viruses. Gastroenteritis is inflammation of the intestines, which causes watery diarrhea, abdominal cramps and pain, nausea, vomiting, muscle aches, headache, and low-grade fever. Symptoms usually last less than a week.

According to the Mayo Clinic, the most common way to develop viral gastroenteritis is through contact with an infected person (sharing utensils, towels, or food) or by ingesting contaminated food or water. Most otherwise healthy people recover without complications. However, for infants, older adults, and people with weak immune systems, viral gastroenteritis can be fatal.

There is no effective treatment for viral gastroenteritis, so prevention is key. In addition to avoiding food and water that may be contaminated, thorough and frequent hand-washing is the best defense.

A number of viruses can cause gastroenteritis. One is noroviruses, which are highly contagious and the most common cause of foodborne illness worldwide. Another is rotaviruses, the most common cause of viral gastroenteritis in children, who are usually infected when they put their fingers or other objects contaminated with the virus into their mouths. Adults infected with rotavirus may not have symptoms, but can still spread the illness.