Bacterial gastroenteritis in adults


What Is It?

Gastroenteritis is an inflammation of the stomach and small intestine that produces diarrhea, cramps, nausea and other symptoms of digestive upset. In adults, the two most common causes of gastroenteritis are viral infections and food poisoning:

  • Viral gastroenteritis — In otherwise healthy adults, viral infections of the digestive tract are often responsible for mild episodes of gastroenteritis. These viral infections include the Norwalk virus, rotaviruses, adenoviruses and other agents. They typically spread when someone either touches an infected person’s stool or touches surfaces contaminated with infected stool. For this reason, health-care personnel and child-care workers have an especially high risk of viral gastroenteritis, particularly if they do not wash their hands thoroughly after dealing with soiled diapers, bedpans or bathroom fixtures. In some circumstances, the agents that cause viral gastroenteritis also can be carried in water or food, especially in drinking water or commercial shellfish that have been contaminated by sewage runoff. Infected food handlers who don’t follow proper sanitary procedures also can spread viral gastroenteritis in meals served in restaurants and cafeterias. Viral gastroenteritis often spreads very easily in institutions and other situations where people live in close quarters, such as prisons, nursing homes, cruise ships, schools, college dorms and public campgrounds.
  • Food poisoning — Food that has been prepared or stored improperly can grow bacteria on its surface, and these bacteria sometimes produce irritating chemicals called toxins. If a person eats the germ-filled food, symptoms of gastroenteritis are triggered either by the bacteria themselves or by their irritating byproducts. Symptoms from a toxin typically begin within a few hours. Symptoms from the bacteria can occur within a few days.

Each year in the United States, millions of people develop gastroenteritis by eating contaminated food, while millions more suffer from mild bouts of viral gastroenteritis. In otherwise healthy adults, both forms of gastroenteritis tend to be mild and brief, and many episodes are never reported to a doctor. However, in the elderly and people with weakened immune defenses, gastroenteritis sometimes can produce dehydration (abnormally low levels of body water) and other dangerous complications. Even in robust adults, certain types of aggressive bacteria occasionally cause more serious forms of food poisoning that can produce high fever and severe gastrointestinal symptoms.


In adults, symptoms of gastroenteritis typically include mild diarrhea (fewer than 10 watery stools daily), cramps, low-grade fever (below 101 degrees Fahrenheit), headache, nausea and sometimes vomiting.


Your doctor will ask whether you recently have been exposed to anyone who has diarrhea, or whether you have recently eaten at a restaurant or social function where the food was left at room temperature for prolonged periods. If you can remember eating a meal within the last week that smelled or tasted strange, be sure to mention it to your doctor.

Since gastroenteritis is especially common where sanitation is poor, your doctor also will ask whether you have recently traveled to an underdeveloped country or to any location where the drinking water is not tested routinely. This includes rural streams, lakes or swimming holes in the United States.

In most cases, your doctor can diagnose mild gastroenteritis based on your symptoms, your history of exposure to spoiled food, impure water or someone with diarrhea, and the results of your physical examination.

Rarely, special laboratory testing may be needed if you have unusually severe symptoms, such as:

  • A fever over 101 degrees Fahrenheit
  • Severe diarrhea (more than 10 watery stools daily)
  • Signs of significant dehydration (dry mouth, intense thirst, weakness)
  • Stool that contains blood or pus

This testing usually involves taking one or more stool samples to be cultured in a laboratory to test for the presence of bacteria (especially campylobacter, salmonella, or E. coli) or examined for microscopic parasites.

Expected Duration

Most cases of mild, uncomplicated gastroenteritis last one to seven days.


To help prevent gastroenteritis, you can:

  • Wash your hands frequently, especially after using the toilet, changing diapers or caring for someone who has diarrhea.
  • Wash your hands before and after preparing food, especially after handling raw meat.
  • Wash diarrhea-soiled clothing in detergent and chlorine bleach. If bathroom surfaces are contaminated with stool, wipe them with a chlorine-based household cleaner.
  • Cook all meat thoroughly before you eat it, and refrigerate leftovers within two hours.
  • Make sure you don’t transfer cooked foods onto unwashed plates that held raw meat.
  • Wash kitchen countertops and utensils thoroughly after they have been used to prepare meat.
  • Never drink unpasteurized milk or untreated water.
  • Drink only bottled water or soft drinks if you travel to an area where sanitation is poor. In these areas, also avoid ice, uncooked vegetables or fruit that you have not peeled yourself.


In otherwise healthy adults, most cases of mild gastroenteritis go away within a few days. You can try the following suggestions until your symptoms subside:

  • To prevent dehydration, drink plenty of fluids — water, soft drinks, sports drinks, broth or over-the-counter, oral-rehydration fluids. If you are too nauseated to drink several ounces at once, try taking many smaller sips over a longer period.
  • Once your nausea starts to subside, gradually resume a normal diet. Begin with clear soups, broth or sweetened gelatin desserts, then build up to rice, rice cereal and more substantial foods. Temporarily avoid milk products and foods that contain wheat flour (bread, macaroni, pizza), since your digestive tract may be unusually sensitive to them for a few days. Also temporarily avoid high-fiber foods, such as fruits, corn and bran.
  • Use over-the-counter antidiarrhea medicines cautiously. These medicines interfere with one of your intestine’s most effective defense mechanisms, the ability to pass harmful bacteria and toxins out of your body through the stool.
  • Rest in bed.

If you have symptoms of severe gastroenteritis, your doctor may prescribe medications to ease your nausea, vomiting and diarrhea; intravenous fluids for symptoms of severe dehydration; and antibiotics if stool tests confirm that a serious bacterial infection is causing your gastroenteritis.

When To Call A Professional

Call your doctor promptly if you have symptoms of gastroenteritis together with any of the following:

  • A fever above 101 degrees Fahrenheit
  • Blood or pus in your stool
  • Diarrhea that lasts more than one week
  • Symptoms of significant dehydration, including dry mouth, intense thirst, and weakness
  • A history of recent travel to a developing country or to any area where sanitation is poor
  • Any medical condition that either weakens the immune system or is treated with immune-suppressing medication

Also, call your doctor promptly if you are taking oral medication for a chronic medical condition and you are either too nauseated to swallow your medicine or have vomited after taking it.


Overall, the prognosis is excellent. Almost all adults with mild gastroenteritis recover completely without complications.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.