Gastroenteritis

Symptoms

Although it's commonly called stomach flu, gastroenteritis isn't the same as influenza. Real flu (influenza) affects 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 salmonella and Escherichia coli (E. coli) or parasites such as giardia.

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.

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

A number of viruses can be the cause of gastroenteritis, including:

• Rotavirus. This is the most common cause of infectious diarrhea in infants and children worldwide — it's also a leading cause of death among children. Every year, thousands of children are hospitalized with complications of the infection. Your child is likely to have rotavirus at least once before age 5. Children are usually infected when they put their fingers or other objects contaminated with the virus into their mouths.Adults who are infected with rotavirus usually don't develop symptoms, but can still spread the illness. Some people, particularly those in institutional settings, may spread the virus even though they don't have any symptoms of illness themselves. A vaccine against rotaviral gastroenteritis is available in some countries, including the United States, and appears to be effective in preventing severe symptoms. Talk to your doctor about whether to immunize your child.
• Noroviruses. There are many different strains of noroviruses, including Norwalk virus, that all cause similar symptoms. In addition to diarrhoea, nausea and vomiting, you may experience muscle aches, headache, fatigue and low-grade fever. Both children and adults are affected by noroviruses. 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. After exposure to the virus, you're likely to feel sick within 18 to 72 hours. Most people feel better in a day or two, but you're still contagious for at least three days — and up to two weeks — after you've recovered.

Risk factors

Gastroenteritis occurs all over the world, affecting people of every age, race and background. In developing nations, it's a leading cause of death in children.

Children in child care centers and older adults living in nursing homes are especially vulnerable. That's because children's immune systems aren't mature until about age 6, and adult immune systems tend to become less efficient later in life.

Intestinal infections can flourish anywhere people congregate — from schools and dormitories to campgrounds and luxury cruise ships. Adults whose resistance is low — often because their immune systems are compromised by HIV, AIDS or other medical conditions — are especially at risk.

Each gastrointestinal virus has a season when it's most active. If you live in the Northern Hemisphere, you're more likely to get rotavirus or the Norwalk virus between October and April.

Complications

Dehydration — a severe loss of water and essential salts and minerals — is the most common serious complication of gastroenteritis. If you're a healthy adult and drink enough to replace fluids you lose from vomiting and diarrhea, dehydration shouldn't be a problem.

But infants, older adults and people with suppressed immune systems may become severely dehydrated when they lose more fluids than they can replace. In that case, they may need to be hospitalized and receive intravenous fluids. In extreme cases dehydration can be fatal.

Diagnosis

Your doctor will likely diagnose gastroenteritis based on symptoms, a physical exam and sometimes on the presence of similar cases in your community. A rapid stool test can detect rotavirus or norovirus, but there are no quick tests for other viruses that cause gastroenteritis. In some cases your doctor may have you submit a stool sample to rule out a possible bacterial or parasitic infection.

References

http://emedicine.medscape.com/article/176515-overview

http://www.healthline.com/health/viral-gastroenteritis

http://www.mayoclinic.org/diseases-conditions/viral-gastroenteritis/basics/definition/con-20019350

http://my.clevelandclinic.org/health/diseases_conditions/hic_Gastroenteritis