Gastroenteritis literally means inflammation of the gastrointestinal tract. Viral gastroenteritis is also called "stomach flu." It is extremely common, especially in children, and is highly contagious. Bacterial gastroenteritis is also known as "food poisoning" and is caused by food that has been prepared or stored improperly. Gastroenteritis can also be caused by ingestion of drugs or chemical toxins (e.g. metals, plant substances).
Viruses such as the norovirus (formerly known as Norwalk virus) cause gastroenteritis. Besides the norovirus, three other viruses are also common causes of gastroenteritis in North America: the rotavirus, the astrovirus, and the adenovirus, which tend to cause disease in infants and young children. They are spread by contaminated feces. From the feces, viruses find their way into food or water, or onto insects or people who later touch and contaminate food (fecal-oral transmission). Unfortunately, these viruses are tough enough to beat modern sanitation practices.
Norovirus is the typical form of gastroenteritis in adults and older children. It can occur at any time of year, but 80% of infections occur between November and April. This virus is spread by the fecal-oral route, and it may also be transmitted from person to person.
Rotavirus mostly affects infants aged 3 to 15 months. Almost all children have been infected by the age of 5 years. It follows a seasonal occurrence, peaking in the late winter and early spring. Adenovirus is the second most common cause of gastroenteritis in children under 2 years of age. It occurs at any time of year, with a slight increase in summer.
Like the adenovirus, astrovirus can infect people of all ages but is most likely to affect infants and young children. It is most common in winter, although it can occur at any time of year.
For infants, diapers are a major source of infection. Germs from the feces can get on both the baby's and the parent's hands.
Viruses cause disease by infecting or irritating cells within the wall of the small intestine. This causes fluids, minerals, and salts to flush into the intestines, leaving the body as diarrhea.
Food poisoning results when a person eats food that has grown bacteria that can cause gastroenteritis. The symptoms of food poisoning are caused either by the bacteria themselves or by the byproducts (toxins) they produce. Symptoms of food poisoning can begin within a few hours or a few days after eating the contaminated food, depending on whether the bacteria or the toxin causes the problem.
Symptoms and Complications
Most people who become infected with these viruses won't have any symptoms, since almost half of these people are immune. The actual rate of infection with these viruses is far higher than the rate of gastroenteritis. Once in a while, an adult will get an infection severe enough to be noticeable. Young children are much more likely to feel symptoms.
Norovirus, when symptomatic, causes the classic "24-hour" gastroenteritis that strikes adults. Symptoms include vomiting and diarrhea. Bowel movements are usually loose and watery, but there is typically no mucus or blood. Low fever, abdominal cramps, aching muscles, and headache are also possible. Both rotavirus and norovirus tend to produce the first symptoms 1 to 3 days after infection. Most people recuperate within 2 or 3 days without any serious or long-lasting health effects.
Young children with rotavirus may have severe watery diarrhea lasting about a week, which can lead to dehydration. Rotavirus also causes vomiting and a significant increase in temperature.
Adenovirus can produce up to 2 weeks of diarrhea for young children, with occasional mild vomiting and sometimes a low fever. It may take over a week before symptoms appear.
Astrovirus creates symptoms similar to a mild rotavirus infection.
Symptoms of food poisoning often include nausea, general weakness or exhaustion, headache, abdominal pain and cramps with abrupt vomiting, and diarrhea. If symptoms last more than 48 hours, your doctor may want to obtain a blood and stool sample as well as to test the food in question.
A young child with fever and diarrhea or vomiting should be seen by a doctor. It is not essential for adults to seek medical advice unless vomiting and diarrhea are severe or medical conditions coexist, as the symptoms usually go away on their own. However, if vomiting or severe diarrhea persist for more than 1 week, call your doctor.
You should also contact your doctor if the following symptoms are present:
- blood in vomit or stool
- a hard, swollen, painful abdomen
- high fever
- excessive thirst, dry mouth
- excessive lethargy
- dizziness or lightheadedness when changing position (e.g., moving from sitting to standing)
Making the Diagnosis
The symptoms are the telltale signs of viral gastroenteritis in adults and older children. Your doctor will ask questions about your symptoms and the length of time you have been experiencing them. They may ask if you've recently been in the hospital or used antibiotics.
Stool testing is done in certain circumstances when the doctor suspects something other than viral gastroenteritis, such as food poisoning. For food poisoning, it is important to pinpoint the likely offender so that others do not become sick from the same food or water.
Treatment and Prevention
Washing hands frequently provides the best defence against the norovirus. This is because exposure to even a small amount of the virus is enough to make you sick. Also, the virus can survive on inanimate objects (such as bathroom sinks, toilets, and doorknobs) and food for extended periods of time – perhaps as long as 12 days.
Wash your hands before and after handling food or food utensils, and after using the toilet, caring for the sick, changing diapers, handling garbage, using the phone, shaking hands, or playing with pets.
Most people do not wash their hands well enough, but following these steps will help keep your hands clean:
- Wet your hands with warm running water.
- Add soap, then rub your hands together to make a soapy lather.
- Continue rubbing your hands together for 20 seconds (about the amount of time it takes to sing through "Twinkle, Twinkle, Little Star" once, not too quickly). Be sure to wash the front and back of your hands as well as between your fingers and under the nails.
- Rinse the hands under running water, letting the water run back into the sink, not down to the elbows.
- Turn off the water using a paper towel to avoid contact with the tap.
- Dry hands thoroughly with a clean towel.
- Use antibacterial gels or hand sanitizers that are now available in most public places, including bathrooms. They can also be purchased at most groceries, pharmacies, and supermarkets and can be carried around for quick and easy use.
If you're infected with the norovirus (or if your child is), stay home from work, daycare or school, as it's easy for others to become infected if they live or work in your environment. Infected people should also not prepare foods while they are sick, and for 3 days afterwards to help reduce the risk of spreading the virus.
There's no cure for gastroenteritis, but symptoms usually go away in a day or two. The important thing is to keep well hydrated, since you're losing fluids. Adults benefit from oral rehydration solutions, broth, or bouillon. A doctor will usually recommend that children under the age of 5 use oral rehydration solutions available at pharmacies. In severe cases, intravenous rehydration may be necessary. Only in very select cases are antibiotics used for treatment.
It's best not to eat anything on the first day of a gastroenteritis infection, as you will likely vomit any food that you eat. Just drink water or other clear fluids or, if you can't tolerate that, suck on chips of ice. When you're feeling slightly better, you may be able to tolerate thin soup.
If you're feeling better the next day, add bland, soft foods such as bananas, soup, crackers, rice, and oatmeal. Smaller meals may also be better tolerated until you're back to normal.
The following are important tips for preventing food poisoning:
- Keep utensils and cooking surfaces clean.
- Always wash your hands before and after preparing food.
- Rinse fruits and vegetables thoroughly.
- Use a cutting board that is smooth, hard, and nonporous. Clean it with soap and water before and after use.
- Make sure all food is cooked thoroughly (especially seafood and poultry).
- Serve foods immediately after they are cooked.