Gastrointestinal infections: what to watch for and what to do

Stomach bugs hit fast and messy. Whether it’s a norovirus at a party, foodborne Salmonella, or traveler's diarrhea from a street vendor, the basics are the same: diarrhea, vomiting, cramps, sometimes fever. You don’t always need a doctor, but knowing when to act and how to safely manage symptoms keeps you out of trouble.

What causes them and common symptoms

Viruses (norovirus, rotavirus) cause most cases. Bacteria like E. coli, Salmonella, Campylobacter, and parasites such as Giardia also cause illness—often linked to undercooked food, raw shellfish, contaminated water, or poor hand hygiene. Typical symptoms: loose stools, stomach cramps, nausea, vomiting, mild fever. Blood in stool, very high fever, or severe belly pain usually means a bacterial cause and needs medical attention.

Dehydration is the biggest risk. Signs include dark urine, very little pee, dizziness, dry mouth, or extreme weakness. Kids and older adults get dehydrated faster—watch them closely.

Practical treatment and when to see a doctor

Start with fluids. Oral rehydration solutions (ORS) are best because they replace salts and sugar in the right balance. If you don’t have ORS, mix 6 teaspoons sugar and half a teaspoon salt in 1 liter of clean water. Sip slowly but steadily. Avoid sugary sodas and alcohol.

Food: eat light and simple once vomiting eases. Plain rice, toast, bananas, and yogurt can help. If lactose intolerance develops after an infection, skip milk for a few days. Over-the-counter options: loperamide (Imodium) can reduce diarrhea in adults without fever or bloody stools. Bismuth subsalicylate (Pepto-Bismol) helps travelers’ diarrhea and nausea for some people. Don’t give aspirin-containing products to children.

Antibiotics are not automatic. They help specific bacterial infections (severe bloody diarrhea, high fever, or confirmed bacterial cause). For traveler's diarrhea with significant symptoms, a short course of azithromycin or another targeted antibiotic may be prescribed—only by a provider.

Probiotics like Lactobacillus rhamnosus GG or Saccharomyces boulardii can shorten illness a bit in many cases. Clinical trials show they often reduce duration by about a day when taken early. They’re safe for most people but check with your doctor if you’re immunocompromised.

Get medical help if you have persistent vomiting, signs of severe dehydration, bloody stool, severe abdominal pain, fever over 39°C (102°F), or symptoms lasting more than 48–72 hours. For infants, the elderly, or anyone with chronic illness, call sooner.

Prevention is simple: wash hands often, cook food thoroughly, avoid raw shellfish and unpasteurized dairy, drink bottled water when traveling in risky areas, and keep sick people away from food preparation. Vaccines exist for rotavirus (infants) and can cut a major cause of severe gastroenteritis.

Bottom line: most stomach bugs get better with fluids, rest, and simple care. Watch for danger signs, use medications carefully, and ask a clinician if symptoms are severe or don’t improve.