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Diarrheal Disease (Acute Gastroenteritis)

Overview

Acute gastroenteritis—commonly called “stomach flu” or “food poisoning”—is an inflammation of the stomach and small intestine that results in a sudden onset of diarrhea, vomiting, abdominal cramps, and fever. It is usually caused by an infectious agent (virus, bacteria, or parasite) and lasts from a few hours to about 10 days. While most healthy adults recover without medical intervention, the condition is a leading cause of morbidity and mortality in children under five and the elderly.

Global impact: The World Health Organization estimates that infectious diarrheal disease accounts for roughly 1.7 billion cases worldwide each year, causing an estimated 525 000 deaths—over 90 % of which occur in low‑ and middle‑income countries.<sup>[1]</sup> In high‑income nations, acute gastroenteritis leads to about 179 million episodes annually, resulting in ~2 million outpatient visits and 200 000 hospitalizations.<sup>[2]</sup>

Symptoms

The clinical presentation varies by pathogen, age, and individual health status. Common symptoms include:

• Watery diarrhea – frequent, loose stools (≥3 per day). Often the first sign.
• Vomiting – may accompany or precede diarrhea; helps expel the irritant.
• Abdominal cramping or pain – colicky or burning sensations.
• Fever – low‑grade (≤38 °C) in most viral cases; higher fevers suggest bacterial infection.
• Headache, muscle aches (myalgia) – especially with viral agents like norovirus.
• Loss of appetite and a general feeling of malaise.
• Blood or mucus in stool – a red flag for invasive bacterial or parasitic infection.
• Dehydration signs – dry mouth, decreased urine output, dizziness, sunken eyes, and rapid heartbeat.

Symptoms usually peak within 24–48 hours and resolve within a week. Persistent diarrhea (>14 days) may indicate a different condition (e.g., inflammatory bowel disease) and warrants further evaluation.

Causes and Risk Factors

Infectious agents

• Viruses (most common)
  • Norovirus – responsible for 20 %–30 % of adult gastroenteritis outbreaks.
  • Rotavirus – leading cause of severe diarrhea in children <5 years; vaccination has reduced incidence by ~80 % in countries with high coverage.<sup>[3]</sup>
  • Adenovirus, astrovirus, and sapovirus – less frequent but notable in daycare settings.
• Bacteria
  • Campylobacter jejuni, Salmonella, Shigella, and Escherichia coli (especially enterotoxigenic E. coli, STEC/EHEC).
  • Clostridioides difficile – often follows antibiotic use.
• Parasites
  • Giardia lamblia, Cryptosporidium, Entamoeba histolytica – more common in travelers and immunocompromised hosts.

Non‑infectious triggers (less common)

• Food intolerances (e.g., lactose intolerance), medication side‑effects (antibiotics, chemotherapy), and inflammatory conditions (Crohn’s disease).

Risk factors

• Age extremes – children <5 years and adults >65 years.
• Immunosuppression – HIV, transplant recipients, chemotherapy.
• Recent antibiotic use – predisposes to C. difficile.
• Close contact settings – schools, nursing homes, cruise ships.
• Poor sanitation, contaminated water/food, and travel to endemic regions.

Diagnosis

For most uncomplicated cases, a clinical diagnosis based on history and physical exam is sufficient. Laboratory testing is reserved for:

• Severe dehydration or electrolyte imbalance.
• Persistent symptoms >7 days.
• High fever, blood/mucus in stool, or immunocompromised status.

Tests commonly used

• Stool culture – isolates bacterial pathogens; takes 24–48 h.
• Multiplex PCR panels – rapid detection of viral, bacterial, and parasitic DNA/RNA (results in <12 h).
• Clostridioides difficile toxin assay – enzyme immunoassay or PCR.
• Stool ova & parasite (O&P) exam – microscopic identification of parasites.
• Serologic tests – rarely needed; useful for certain viral infections (e.g., rotavirus IgA).
• Blood work – CBC, electrolytes, BUN/creatinine if dehydration is suspected.

Treatment Options

General measures

• Rehydration – the cornerstone of therapy.
  • Oral rehydration salts (ORS) solution: 1 L water + 6 g glucose + 2.5 g sodium (commercial ORS packets are convenient).
  • For mild cases, clear fluids (broth, diluted juice, oral rehydration solutions) are adequate.
  • Severe dehydration requires intravenous (IV) isotonic fluids (e.g., normal saline or lactated Ringer’s).
• Dietary adjustments – the BRAT diet (bananas, rice, applesauce, toast) is a traditional suggestion, but current guidance from the CDC encourages returning to a normal, balanced diet as tolerated.
• Rest and isolation – limit contact with others for at least 48 h after symptom resolution (especially with norovirus).

Pharmacologic therapy

• Antimotility agents (e.g., loperamide) – can reduce stool frequency in non‑bloody, non‑febrile diarrhea. Avoid in suspected C. difficile or invasive bacterial infection.
• Antibiotics – indicated only for certain bacterial etiologies:
  • Campylobacter: azithromycin 500 mg single dose or 1 g once daily for 3 days.
  • Shigella: ciprofloxacin 500 mg BID for 3 days or azithromycin 500 mg daily for 3 days.
  • Travelers’ diarrhea (ETEC): a short course of azithromycin or ciprofloxacin.
  • C. difficile: oral vancomycin 125 mg QID for 10 days (or fidaxomicin).
• Probiotics – meta‑analyses suggest modest benefit in reducing duration of viral and antibiotic‑associated diarrhea (e.g., Lactobacillus rhamnosus GG, Saccharomyces boulardii). Choose strains with proven efficacy and discuss with a clinician if immunocompromised.

When to consider hospitalization

• Severe dehydration (≥10 % body weight loss), hypotension, or shock.
• Persistent vomiting preventing oral intake.
• High fever (>39 °C) or signs of systemic infection.
• Electrolyte abnormalities (e.g., hyponatremia, hypokalemia).
• Immunocompromised patients or those with underlying chronic disease.

Living with Diarrheal Disease (Acute Gastroenteritis)

Day‑to‑day management

• Hydration schedule – sip 250 mL (8 oz) of ORS or clear fluids every 15 minutes; adjust based on urine output (aim for pale yellow urine).
• Monitor weight daily; a loss >2 kg in an adult or >5 % of body weight in a child signals worsening dehydration.
• Maintain good hand hygiene: wash hands with soap for at least 20 seconds after bathroom use and before handling food.
• Avoid dairy, caffeine, alcohol, and high‑fiber foods until diarrhea improves.
• Use a separate bathroom if possible; disinfect surfaces with a bleach solution (1 tbsp bleach per quart water) after each episode.
• Educate family members on proper food storage—keep perishable foods refrigerated (<4 °C) and discard any leftovers after 2 hours at room temperature.

Special considerations for children

• Offer small, frequent sips of ORS or breast milk.
• Watch for “wet diapers” to gauge hydration.
• Do not give over‑the‑counter anti‑diarrheal drugs to children under 2 years.

Prevention

• Vaccination – Rotavirus vaccine (RotaTeq® or Rotarix®) is recommended for infants; it reduces severe gastroenteritis hospitalizations by ~85 %.<sup>[4]</sup>
• Hand hygiene – Handwashing with soap and water is more effective than alcohol‑based rubs against norovirus.
• Safe food handling
  • Cook meats to internal temperatures: poultry 74 °C, ground beef 71 °C.
  • Wash fruits and vegetables under running water.
  • Avoid raw or undercooked shellfish.
• Water safety – Use filtered, boiled, or chlorinated water in areas with questionable supply; disinfect wells annually.
• Travel precautions – Use bottled water, avoid ice, and eat only hot‑cooked foods when traveling to high‑risk regions.
• Avoid unnecessary antibiotics – Reduces risk of C. difficile infection.

Complications

If untreated or inadequately managed, acute gastroenteritis can lead to:

• Severe dehydration – may cause acute kidney injury, hypotensive shock, or electrolyte disturbances (e.g., hyponatremia, hypokalemia).
• Electrolyte imbalance – can precipitate cardiac arrhythmias, especially in the elderly.
• Secondary bacterial infection – particularly after viral gastroenteritis in immunocompromised hosts.
• Hemolytic uremic syndrome (HUS) – a rare but life‑threatening complication of Shiga‑toxin producing E. coli (STEC).
• Reactive arthritis – may follow Campylobacter or Salmonella infection.
• Chronic post‑infectious irritable bowel syndrome (IBS) – persistent abdominal pain and altered bowel habits after the acute phase.

When to Seek Emergency Care

References

1. World Health Organization. Diarrhoeal disease Fact Sheet. 2023.
2. Centers for Disease Control and Prevention. Epidemiology of Diarrhea. Updated 2024.
3. Mayo Clinic. Rotavirus. Review 2024.
4. Cleveland Clinic. Rotavirus Infection. 2024.

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