What is the treatment approach for infectious vs viral diarrhea?

Treatment of Infectious vs Viral Diarrhea

For most cases of acute diarrhea—whether bacterial or viral—antibiotics are NOT recommended; the cornerstone of treatment is oral rehydration solution (ORS) for all etiologies, with antibiotics reserved only for specific high-risk scenarios including bloody diarrhea with fever, suspected Shigella dysentery, immunocompromised patients, or recent international travelers with fever ≥38.5°C. 1, 2

Key Principle: Etiology Rarely Changes Management

The distinction between "infectious" (bacterial) and "viral" diarrhea is less clinically relevant than understanding that most acute diarrhea is self-limited regardless of cause and requires only supportive care. 3, 4 The critical decision is identifying the minority of patients who need antibiotics based on clinical presentation, not microbiologic etiology. 5

Universal First-Line Treatment (All Etiologies)

Oral rehydration solution (reduced osmolarity ORS) is the first-line therapy for mild to moderate dehydration in all patients with acute diarrhea from any cause—bacterial, viral, or parasitic. 1

• Administer ORS until clinical dehydration is corrected, then continue as maintenance to replace ongoing stool losses 1
• Escalate to intravenous fluids (lactated Ringer's or normal saline) only for severe dehydration, shock, altered mental status, or ileus 1
• Resume age-appropriate diet immediately after rehydration is completed 1
• Continue breastfeeding throughout the illness in infants 1

When Antibiotics Are NOT Indicated

In immunocompetent patients with acute watery diarrhea without recent international travel, empiric antimicrobial therapy is not recommended. 1, 2 This applies to most viral gastroenteritis and many bacterial causes. 3, 4

For bloody diarrhea in immunocompetent children and adults, empiric antibiotics while awaiting diagnostic results are NOT recommended. 1 The self-limited nature of most cases, cost, and antibiotic resistance concerns outweigh potential benefits. 3

Critical contraindication: NEVER give antibiotics for suspected or confirmed STEC O157:H7 or Shiga toxin 2-producing E. coli, as this significantly increases risk of hemolytic uremic syndrome (HUS). 1, 6

Specific Scenarios Requiring Antibiotics

Bloody Diarrhea with High-Risk Features

Antibiotics ARE indicated for immunocompetent patients with bloody diarrhea ONLY in these situations: 1

• Infants <3 months of age with suspected bacterial etiology → treat with third-generation cephalosporin 1, 6
• Bacillary dysentery (frequent scant bloody stools, fever, abdominal cramps, tenesmus) presumptively due to Shigella → treat with antibiotics 1
• Recent international travelers with temperature ≥38.5°C and/or signs of sepsis → treat empirically 1
• Immunocompromised patients with severe illness and bloody diarrhea → treat with antibiotics 1, 2

Antibiotic Selection

For adults: Fluoroquinolone (ciprofloxacin) or azithromycin, depending on local susceptibility patterns and travel history 1, 2, 7

For children: 1, 6

• Third-generation cephalosporin (ceftriaxone) for infants <3 months or those with neurologic involvement
• Azithromycin for older children based on local susceptibility patterns and travel history

Enteric Fever

Patients with clinical features of sepsis and suspected enteric fever should receive empiric broad-spectrum antibiotics after obtaining blood, stool, and urine cultures. 1, 2 Narrow therapy once susceptibility results are available. 1

Ancillary Therapies

Antimotility agents (loperamide) should NOT be given to children <18 years of age with acute diarrhea. 1 In adults, loperamide may be used for acute watery diarrhea once adequately hydrated, but avoid in inflammatory diarrhea or diarrhea with fever due to toxic megacolon risk. 1

Antiemetics (ondansetron) may be given to children >4 years and adolescents to facilitate oral rehydration tolerance. 1

Probiotics may be offered to reduce symptom severity and duration in immunocompetent patients. 1

Zinc supplementation reduces diarrhea duration in children 6 months to 5 years in areas with high zinc deficiency prevalence or malnutrition. 1

When to Reassess

Modify or discontinue antibiotics when a specific pathogen is identified. 1, 2

Consider non-infectious causes (inflammatory bowel disease, irritable bowel syndrome, lactose intolerance) in patients with symptoms lasting ≥14 days. 1, 6

Reassess fluid and electrolyte balance, nutritional status, and antibiotic efficacy in patients with persistent symptoms. 1, 2

Common Pitfalls to Avoid

• Do not treat asymptomatic contacts of patients with diarrhea; advise infection control measures only 1, 2
• Do not routinely obtain follow-up stool testing after symptom resolution for case management 1, 2
• Do not use antibiotics as a substitute for adequate hydration—rehydration is the priority regardless of etiology 1, 8
• Avoid empiric antibiotics in persistent watery diarrhea lasting ≥14 days without further evaluation 1