Gastroenteritis: Infectious and Noninfective Causes and Treatment

Symptoms

• watery diarrhea, sometimes several times an hour at first
• nausea and vomiting
• stomach cramps and bloating
• low-grade fever, chills, aches and headache
• loss of appetite and tiredness

Symptoms of viral gastroenteritis typically start 12 to 48 hours after exposure.

Infectious gastroenteritis

Viruses (most common)

• Norovirus: the leading cause of gastroenteritis in all ages in the US. Sudden vomiting and diarrhea lasting 1 to 3 days. Extremely contagious; outbreaks on cruise ships, in schools and care homes. See viral gastroenteritis.
• Rotavirus: severe watery diarrhea in young children; now much less common thanks to vaccination.
• Adenovirus and astrovirus: mainly in children.

Bacteria

• Salmonella (poultry, eggs): see Salmonella gastroenteritis
• Campylobacter (undercooked chicken, unpasteurized milk)
• E. coli, including Shiga toxin-producing strains that can cause bloody diarrhea and kidney failure in children
• Shigella (person-to-person spread, bloody diarrhea)
• Clostridioides difficile after antibiotics: see C. difficile colitis
• toxins from Staphylococcus aureus or Bacillus cereus in food, causing food poisoning with rapid vomiting

Parasites

Giardia and Cryptosporidium from contaminated water cause prolonged diarrhea, bloating and gas. Common after travel, camping or swimming pool exposure. See traveler's diarrhea.

Noninfective gastroenteritis: causes

Gastroenteritis without an infection is called noninfective (or noninfectious) gastroenteritis. See noninfectious gastroenteritis for more detail. Common causes:

Noninfective gastroenteritis is not contagious. It often lasts longer or recurs, and the cause must be identified to stop it.

Who is at higher risk of complications

• babies and young children
• adults over 65
• pregnant people
• people with weakened immune systems, kidney disease or diabetes
• people taking diuretics, ACE inhibitors, ARBs, SGLT2 inhibitors or metformin, which can worsen dehydration or kidney problems (ask a doctor or pharmacist about pausing them during severe illness)

Diagnosis

Most cases need no tests. Doctors check for dehydration and consider tests when:

• there is blood in the stool, high fever or severe illness
• symptoms last more than a week
• there was recent travel, antibiotic use or hospitalization
• there is an outbreak

Tests include stool cultures or multiplex PCR panels, C. difficile tests, blood tests for electrolytes and kidney function, and, for noninfective causes, celiac antibodies, fecal calprotectin, a medication review, and sometimes colonoscopy with biopsies.

Treatment

Rehydration

• oral rehydration solution (ORS): the best choice for moderate fluid loss; small, frequent sips if vomiting
• for mild illness in adults, water, broth and diluted juice are fine
• keep breastfeeding babies; formula-fed babies continue formula plus ORS as needed
• IV fluids in hospital for severe dehydration

Eating

Return to normal food as soon as you feel able. Starting with bland foods (rice, toast, bananas, crackers, soup) is fine, but strict diets are not necessary. Avoid alcohol and very fatty or sugary foods for a few days.

Medicines

• loperamide can reduce diarrhea in adults without fever or bloody stools; follow the label dose and do not give to young children
• bismuth subsalicylate can ease symptoms in adults; it can turn stools black; avoid in children and teenagers because it contains a salicylate
• anti-nausea medicine such as ondansetron may be prescribed, especially for children
• antibiotics are needed only for some bacterial infections, severe illness or high-risk patients; they can worsen Shiga toxin E. coli
• noninfective causes: stop or change the offending medicine, avoid trigger foods, or treat the underlying condition

Prevention

• wash hands with soap and water, especially after the toilet and before food; alcohol gel does not reliably kill norovirus
• clean contaminated surfaces with a bleach-based cleaner
• stay home for 48 hours after symptoms stop, and do not prepare food for others
• cook meat thoroughly, avoid unpasteurized milk, and wash produce
• rotavirus vaccine for infants

Frequently asked questions

What is noninfective gastroenteritis?

Noninfective gastroenteritis is inflammation of the stomach and intestines that is not caused by a virus, bacterium or parasite. Common causes include medicines such as NSAIDs or antibiotics, food intolerances or allergies, alcohol, toxins, radiation and inflammatory bowel conditions.

What causes noninfective gastroenteritis?

Typical causes are medicines (NSAIDs, metformin, antibiotics, chemotherapy), lactose or other food intolerances, food allergies, alcohol, chemical or plant toxins, radiotherapy and conditions such as microscopic colitis, celiac disease or Crohn's disease.

How is noninfective gastroenteritis treated?

Treatment focuses on fluids to prevent dehydration and on removing the cause: stopping or changing a medicine, avoiding trigger foods, or treating an underlying condition. Antibiotics do not help. Persistent symptoms need tests to find the cause.

How long does gastroenteritis last?

Viral gastroenteritis usually lasts 1 to 3 days, though some people feel tired for a week. Bacterial infections can last up to a week. Diarrhea lasting more than 7 days, or recurring, suggests another cause and needs medical review.

Is gastroenteritis contagious?

Infectious gastroenteritis is very contagious, especially norovirus, which spreads through vomit, stool, contaminated food and surfaces. People can spread it for at least 48 hours after symptoms stop. Noninfective gastroenteritis is not contagious.