"Stomach flu" is the commonly used name for gastroenteritis. Gastroenteritis is almost always caused by a virus. But it is not caused by the influenza virus.

The viruses that most often cause gastroenteritis are noroviruses and rotaviruses, but there are host of other viruses. Some bacteria and parasites also can be the culprit.

The usual symptoms of gastroenteritis include:

• Diarrhea
• Abdominal discomfort, usually cramps
• An upset stomach
• Nausea, occasionally with vomiting

Gastroenteritis may cause a low fever and mild headache.

Viral gastroenteritis goes away without medication. The main concern until it goes away is dehydration. You can avoid this by drinking plenty of fluids.

Viral gastroenteritis is highly contagious, but it is not airborne. It spreads from person to person by direct contact.

These viruses can survive in food and beverages. Food becomes contaminated most often when people do not wash their hands (or wash them poorly) after using the bathroom.

This is why buffets can infect many people. This has been the problem with outbreaks on cruise ships.

Other sources of viral contamination are drinking water and seafood that has been exposed to untreated sewage.