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Stomach Infection Symptoms: What's Causing It and What to Do

"Stomach infection" is a broad term that most people use to describe anything that causes abdominal discomfort, diarrhoea, nausea, or vomiting. The umbrella is wide enough to cover half a dozen different conditions — from a 24-hour viral gastroenteritis to chronic H. pylori infection to amoebic dysentery — and they're managed differently.

Knowing the difference matters because it determines whether you need rest and ORS, a specific antibiotic, or an urgent visit to a doctor.

The Main Types of Stomach Infection in India

1. Viral gastroenteritis ("stomach bug")

The most common cause of sudden vomiting and diarrhoea. Caused by norovirus, rotavirus (particularly in children), and other enteric viruses. Spreads through contaminated food, water, or contact with an infected person.

Characteristics:

• Sudden onset of nausea, vomiting, and/or diarrhoea
• Typically lasts 24–72 hours
• Fever may or may not be present — if present, usually low-grade
• No blood or mucus in stool
• The entire household may be affected if the source is shared food or water
• Resolves on its own with hydration and rest — no antibiotic needed

2. Bacterial gastroenteritis (food poisoning)

Caused by Salmonella, E. coli, Staphylococcus aureus, Campylobacter, or others from contaminated food. Generally produces more intense symptoms than viral gastroenteritis, and some bacterial types can cause prolonged illness.

Characteristics:

• Onset 1–72 hours after eating contaminated food (depending on organism)
• Vomiting often prominent
• Diarrhoea — can be very frequent and large volume
• Fever — more likely and more significant than viral
• Blood in stool is possible with certain organisms (E. coli O157, Salmonella, Shigella)
• Duration: 2–5 days for most, longer with some organisms

3. Amoebic infection (amoebiasis)

Caused by Entamoeba histolytica, a parasite transmitted through contaminated water or food. Very common in India. Can cause acute dysentery or become chronic.

Characteristics:

• Diarrhoea with blood and mucus ("amoebic dysentery") — the characteristic red-and-white appearance of stool
• Abdominal cramping and pain, often in the right lower abdomen
• Tenesmus — a persistent feeling of needing to pass stool even after the bowel has emptied
• Fever — may be absent or low-grade
• Can become chronic — weeks to months of intermittent loose stools without dramatic acute illness
• Can spread to the liver (amoebic liver abscess) — causing right upper abdominal pain, high fever, and weight loss — a serious complication
• Requires specific treatment with metronidazole (tinidazole) — does NOT resolve with standard antibiotics for bacterial infection

4. Giardiasis

Caused by Giardia lamblia, a parasite from contaminated water. Common in areas with untreated drinking water.

Characteristics:

• Explosive, foul-smelling, watery or greasy diarrhoea
• Significant bloating and gas
• Abdominal cramps
• Notably absent: blood in stool (unlike amoebic dysentery)
• No significant fever
• Can persist for weeks — chronic giardiasis produces prolonged loose stools, bloating, and weight loss
• Treatment: metronidazole or tinidazole

5. H. pylori gastritis

Helicobacter pylori is a bacterium that infects the stomach lining. Prevalence in India is extremely high — estimates suggest 40–70% of adults carry H. pylori. Most infected people never develop symptoms, but in others it causes:

Characteristics:

• Upper abdominal pain or burning (epigastric pain) — often in the fasting state, relieved by eating, or worse with spicy food
• Nausea
• Bloating after meals
• Burping
• Loss of appetite
• In some, progresses to peptic ulcer (gastric or duodenal) — causing more intense episodic pain, sometimes vomiting

H. pylori is the leading cause of peptic ulcers and a significant risk factor for stomach cancer with long-term untreated infection. It's diagnosed by a urea breath test, stool antigen test, or endoscopy biopsy, and treated with triple antibiotic therapy combined with a proton pump inhibitor.

6. Salmonella infection (excluding typhoid)

Non-typhoidal Salmonella (from undercooked chicken and eggs, contaminated dairy) causes gastroenteritis, not the sustained systemic illness of typhoid fever.

Characteristics:

• Onset 6–48 hours after eating contaminated food
• Diarrhoea, often watery, sometimes bloody
• Nausea and vomiting
• Fever — usually more significant than simple viral gastroenteritis
• Abdominal cramps
• Duration: 4–7 days; longer in immunocompromised
• Treatment: most cases resolve without antibiotics; antibiotics (azithromycin or fluoroquinolone) for severe cases or high-risk patients

7. Typhoid fever

A separate and more severe systemic infection (see dedicated blog) — causes a sustained high fever, stepwise fever pattern, headache, and ultimately involves the entire body, not just the gut.

Symptoms That Distinguish Different Stomach Infections

| Symptom | Viral | Bacterial | Amoeba | Giardia | H. pylori | |---|---|---|---|---|---| | Onset | Sudden | Sudden | Gradual | Gradual | Chronic | | Vomiting | Prominent | Common | Less common | Uncommon | Nausea only | | Diarrhoea | Watery | Watery/bloody | Bloody + mucus | Greasy, foul | No/mild | | Fever | Low/absent | Often present | Low/absent | Absent | Absent | | Blood in stool | No | Sometimes | Yes (dysentery) | No | No | | Bloating | Mild | Mild | Moderate | Severe | Common | | Duration | 1–3 days | 2–5 days | Weeks (chronic) | Weeks | Chronic |

When to Manage at Home

Suitable for home management if:

• Diarrhoea is watery (not bloody) and vomiting is settling
• No fever above 38.5°C
• Can tolerate fluids orally — small sips are staying down
• Urinating at least 4 times in 24 hours (adequate hydration)
• Symptoms are improving after 24 hours
• No significant underlying health conditions (diabetes, kidney disease, immunocompromised)

At home:

ORS is the priority. Small, frequent sips — a few teaspoons every few minutes when vomiting is present, larger amounts once vomiting settles. Coconut water is an excellent electrolyte replacement. Rice water (kanji) and plain clear soup also help.

Begin bland, easily digestible food as soon as appetite allows:

• Plain rice and khichdi
• Banana — pectin helps firm stool; potassium replaces what's lost
• Curd — probiotics support gut recovery; fine to start once vomiting has stopped
• Plain boiled potato
• Toast or plain biscuits

Rest. The gut recovers faster with rest.

Do not take antibiotics without diagnosis. Most stomach infections are viral. Antibiotics don't help viral infections. For bacterial infections, the specific bacteria determines which antibiotic is appropriate — inappropriate antibiotics (like amoxicillin for a Salmonella infection) do more harm than good.

When to See a Doctor

Seek medical attention if:

• Blood or mucus in the stool — needs stool examination to identify the cause
• Fever above 38.5°C with diarrhoea
• Diarrhoea is more than 6 large watery stools in 24 hours
• Vomiting is preventing any fluid retention for more than 6 hours
• Signs of dehydration — no urination in 8 hours, very dark urine, extreme weakness, dizziness on standing
• Symptoms are getting worse, not better, after 48 hours
• Pain is severe or localised (rather than diffuse cramping) — to rule out appendicitis, cholecystitis, pancreatitis
• Symptoms in a diabetic, elderly person, infant under 6 months, or someone who is immunocompromised — these groups dehydrate rapidly and tolerate infection less well
• Symptoms consistent with amoebic dysentery (bloody diarrhoea with mucus, right-sided abdominal pain, persisting beyond a few days) — requires specific treatment
• Abdominal pain that is severe and constant (not cramping in waves) — may indicate a surgical emergency

Investigation and Diagnosis

For presentations requiring medical evaluation:

Stool examination (routine and culture): detects bacteria, cysts of amoeba and Giardia, blood, and mucus. The most directly useful test for persistent or bloody diarrhoea.

Complete blood count: high white blood cell count suggests bacterial or parasitic infection; normal count is more consistent with viral.

Blood culture: if typhoid or bacteraemia (bacteria in the bloodstream) is suspected.

Urea breath test or stool antigen test: specifically for H. pylori detection.

Upper endoscopy (gastroscopy): if H. pylori gastritis or peptic ulcer is suspected — allows direct visualisation and biopsy.

Ultrasound of abdomen: if amoebic liver abscess is suspected (right upper abdominal pain, high fever in someone with recent or ongoing amoebic infection).

Treatment by Type

Viral gastroenteritis: ORS, rest, probiotics, bland diet. No antibiotic. Zinc supplementation for children under 5.

Bacterial gastroenteritis (mild): ORS, rest, close monitoring. Antibiotics only for severe cases or high-risk patients.

Amoebic dysentery: metronidazole (tinidazole) for 5–7 days, followed by diloxanide furoate to eliminate intestinal cysts and prevent relapse.

Giardiasis: metronidazole or tinidazole — single-dose tinidazole is effective and well-tolerated.

H. pylori: triple therapy — typically two antibiotics (amoxicillin + clarithromycin, or amoxicillin + metronidazole, or bismuth-containing quadruple therapy) plus a proton pump inhibitor (omeprazole, pantoprazole) for 10–14 days.

Non-typhoidal Salmonella: most cases manage with supportive care. Azithromycin or fluoroquinolone for severe cases.

A Word on Chronic Stomach Problems

If you have recurrent or persistent upper abdominal discomfort, bloating, acidity, and nausea that has been going on for weeks or months — this is unlikely to be an acute infection. H. pylori gastritis, functional dyspepsia, IBS, or other conditions are more likely. These need investigation, not repeated courses of antibiotics.

Recurrent bloody diarrhoea or persistent loose stools for more than 4 weeks warrants colonoscopy evaluation to look for inflammatory bowel disease or other causes.

Care at Prakash Hospital Noida

At Prakash Hospital Noida, our physicians evaluate gastrointestinal infections with stool examination, blood tests, H. pylori testing, and ultrasound where indicated. IV rehydration for significant dehydration, antiparasitic and antibiotic treatment based on confirmed diagnosis, and specialist gastroenterology assessment for chronic or complex cases are all available.

Whether you live in Sector 18, Sector 62, Greater Noida West, or anywhere in the NCR, Prakash Hospital Noida is a trusted name for gastroenterology, stomach infection treatment, and digestive health in Noida.

To book a consultation, call the number.

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