Viral gastroenteritis is commonly referred to as the stomach flu -- although this name is misleading because the illness is not caused by the influenza virus, the culprit for the flu. Several viruses can cause gastroenteritis, though norovirus is by far the most likely culprit for an illness that lasts only a day or two. Norovirus causes an estimated 19 to 21 million cases of gastroenteritis each year, according to the Centers for Disease Control and Prevention. Cases peak in the winter months, but outbreaks can occur anytime. Washing your hands often and avoiding contact with people who are sick are the most effective ways to prevent a stomach virus.
Nausea and Vomiting
Norovirus infection dramatically slows gastric emptying, meaning the rate at which food and liquids pass from the stomach to the intestines. This effect, in combination with inflammation of the stomach and small intestine, is believed to trigger nausea and often vomiting, which can be severe. As a rule of thumb, it's best to avoid eating or drinking anything for at least an hour after vomiting. After you've let your stomach rest, you can try a small sip of water every 15 to 20 minutes. Continue with small sips for 3 to 4 hours before increasing your fluid intake, as putting too much in your stomach could aggravate your nausea and restart the vomiting.
Abdominal Cramps and Diarrhea
Norovirus causes watery diarrhea, typically accompanied by abdominal cramps. The diarrhea and cramps occur because the infection temporarily disrupts the activity of some digestive enzymes in the upper portion of the small intestine. Other related symptoms include bloating, passage of excessive amounts of gas along with the watery stool, and audible gurgling noises from the intestines. Unfortunately, it's relatively common for people with norovirus to experience vomiting and diarrhea at the same time -- a truly miserable situation. The good news is that the intestine recovers from this temporary disruption of function very quickly and without treatment.
Gastroenteritis due to norovirus sometimes causes other symptoms, including a low fever, headache and body aches. Dehydration due to severe nausea and vomiting can lead to additional signs and symptoms, such as: -- dry, sticky mouth and intense thirst -- dark urine and reduced frequency of urination -- dizziness when getting up to a standing position -- worsening nausea, vomiting and headache
Warnings and Precautions
As miserable as a bout with a 24-hour stomach virus is, most people are back to normal in a day or two. Call your doctor if you experience symptoms of dehydration, especially if you have an ongoing medical condition, such as diabetes or heart disease. Sometimes an illness that initially seems like a stomach virus is actually another, more serious ailment. Seek medical care as soon as possible if you experience any possible alarm symptoms, including: -- vomiting blood or material that looks like coffee grounds -- severe or worsening abdominal pain -- vomiting but unable to pass stool or gas -- symptoms persist for more than a couple of days without improvement -- bloody or tar-colored stools -- high fever
Reviewed and revised by: Tina M. St. John, M.D.
- Centers for Disease Control and Prevention: Norovirus Clinical Overview
- Merck Manual Professional Version: Overview of Gastroenteritis
- Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 8th Edition; John E. Bennett, et al.
- Centers for Disease Control and Prevention: Rotavirus Clinical Information
- Centers for Disease Control and Prevention: Norovirus: U.S. Trends and Outbreaks
- Viruses: Pathogenesis of Noroviruses, Emerging RNA Viruses