Viral gastroenteritis (stomach flu)

DEFINITION

Viral gastroenteritis is an intestinal infection marked by watery diarrhea, abdominal cramps, nausea or vomiting, and sometimes fever.

The most common way to develop viral gastroenteritis — often called stomach flu — is through contact with an infected person or by ingesting contaminated food or water. If you’re otherwise healthy, you’ll likely recover without complications. But for infants, older adults and people with compromised immune systems, viral gastroenteritis can be deadly.

There’s 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-washings are your best defense.

CAUSES

You’re most likely to contract viral gastroenteritis when you eat or drink contaminated food or water, or if you share utensils, towels or food with someone who’s infected.

A number of viruses can cause gastroenteritis, including:

• Noroviruses. Both children and adults are affected by noroviruses, the most common cause of foodborne illness worldwide. Norovirus infection can sweep through families and communities. It’s especially likely to spread among people in confined spaces. In most cases, you pick up the virus from contaminated food or water, although person-to-person transmission also is possible.
• Rotavirus. Worldwide, this is 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. The infection is most severe in infants and young children. Adults infected with rotavirus may not have symptoms, but can still spread the illness — of particular concern in institutional settings because infected adults unknowingly can pass the virus to others. A vaccine against viral gastroenteritis is available in some countries, including the United States, and appears to be effective in preventing the infection.

Some shellfish, especially raw or undercooked oysters, also can make you sick. Although contaminated drinking water is a cause of viral diarrhea, in many cases the virus is passed through the fecal-oral route — that is, someone with a virus handles food you eat without washing his or her hands after using the toilet.

SYMPTOMS

Although it’s commonly called stomach flu, gastroenteritis isn’t the same as influenza. Real flu (influenza) affects only your respiratory system — your nose, throat and lungs. Gastroenteritis, on the other hand, attacks your intestines, causing signs and symptoms, such as:

• Watery, usually nonbloody diarrhea — bloody diarrhea usually means you have a different, more severe infection
• Abdominal cramps and pain
• Nausea, vomiting or both
• Occasional muscle aches or headache
• Low-grade fever

Depending on the cause, viral gastroenteritis symptoms may appear within one to three days after you’re infected and can range from mild to severe. Symptoms usually last just a day or two, but occasionally they may persist as long as 10 days.

Because the symptoms are similar, it’s easy to confuse viral diarrhea with diarrhea caused by bacteria, such as Clostridium difficile, salmonella and E. coli, or parasites, such as giardia.

When to see a doctor

If you’re an adult, call your doctor if:

• You’re not able to keep liquids down for 24 hours
• You’ve been vomiting for more than two days
• You’re vomiting blood
• You’re dehydrated — signs of dehydration include excessive thirst, dry mouth, deep yellow urine or little or no urine, and severe weakness, dizziness or lightheadedness
• You notice blood in your bowel movements
• You have a fever above 104 F (40 C)

For infants and children

See your doctor right away if your child:

• Has a fever of 102 F (38.9 C) or higher
• Seems lethargic or very irritable
• Is in a lot of discomfort or pain
• Has bloody diarrhea
• Seems dehydrated — watch for signs of dehydration in sick infants and children by comparing how much they drink and urinate with how much is normal for them

If you have an infant, remember that while spitting up may be an everyday occurrence for your baby, vomiting is not. Babies vomit for a variety of reasons, many of which may require medical attention.

Call your baby’s doctor right away if your baby:

• Has vomiting that lasts more than several hours
• Hasn’t had a wet diaper in six hours
• Has bloody stools or severe diarrhea
• Has a sunken soft spot (fontanel) on the top of his or her head
• Has a dry mouth or cries without tears
• Is unusually sleepy, drowsy or unresponsive