What is the recommended treatment for a patient presenting with symptoms of enteric virus infection, including diarrhea, vomiting, abdominal cramps, and fever?

Treatment of Enteric Virus Infection

For patients with enteric viral gastroenteritis presenting with diarrhea, vomiting, abdominal cramps, and fever, the cornerstone of treatment is oral rehydration therapy with reduced osmolarity oral rehydration solution (ORS), while antimicrobial therapy should be avoided in most cases unless specific bacterial infection is suspected or the patient meets high-risk criteria. 1

Primary Treatment: Rehydration

Reduced osmolarity ORS is the first-line therapy for mild to moderate dehydration in all age groups with viral gastroenteritis. 1, 2 This should be initiated immediately upon presentation, as viral gastroenteritis causes death primarily through dehydration. 3

Rehydration Protocol by Severity

Mild to Moderate Dehydration:

• Administer ORS 50-100 mL/kg over 3-4 hours in infants and children, or 2-4 L in adolescents and adults 2
• Children <10 kg: give 60-120 mL ORS after each diarrheal stool or vomiting episode (maximum ~500 mL/day) 2
• Children >10 kg: give 120-240 mL ORS after each episode (maximum ~1 L/day) 2
• Adolescents and adults: ad libitum ORS up to ~2 L/day 2
• Oral rehydration is successful in more than 90% of cases when given in frequent, small amounts over 3-4 hours 4

Severe Dehydration:

• Administer isotonic intravenous fluids (lactated Ringer's or normal saline) when there is severe dehydration, shock, altered mental status, or ileus 1, 2
• Give IV boluses of 20 mL/kg until pulse, perfusion, and mental status normalize 2
• Continue IV rehydration until the patient awakens, has no aspiration risk, and has no evidence of ileus 1
• Once stabilized, transition to ORS for remaining deficit replacement 1

Nasogastric Administration:

• Consider nasogastric ORS for patients with moderate dehydration who cannot tolerate oral intake or children with normal mental status who are too weak or refuse to drink 1, 2

Nutrition Management

Resume age-appropriate diet during or immediately after rehydration is completed. 1, 2 Continue human milk feeding in infants throughout the diarrheal episode. 1 This approach prevents nutritional insult from anorexia, vomiting, and malabsorption. 3

When Antimicrobials Are NOT Indicated

In most patients with acute watery diarrhea consistent with viral gastroenteritis, empiric antimicrobial therapy is not recommended. 1, 5 Since acute diarrhea is most often self-limited and caused by viruses, routine antibiotic use is inappropriate for most adults with mild, watery diarrhea. 5

Exceptions: When to Consider Antimicrobials

Consider empiric antimicrobial therapy only in these specific scenarios:

High-Risk Patients:

• Infants <3 months of age with suspicion of bacterial etiology 1, 6
• Immunocompromised patients with severe illness and bloody diarrhea 1, 6
• Patients >65 years who are severely ill or septic 5

Clinical Presentations Suggesting Bacterial Infection:

• Ill patients with documented fever in medical setting, abdominal pain, bloody diarrhea, and bacillary dysentery (frequent scant bloody stools, fever, abdominal cramps, tenesmus) presumptively due to Shigella 1, 6
• Recent international travelers with body temperature ≥38.5°C and/or signs of sepsis 1, 6
• Clinical features of enteric fever (sepsis with suspected Salmonella typhi/paratyphi) 1, 6

Empiric Antimicrobial Choices When Indicated:

• Adults: fluoroquinolone (ciprofloxacin) or azithromycin based on local susceptibility patterns and travel history 1, 2
• Children: third-generation cephalosporin for infants <3 months or those with neurologic involvement; otherwise azithromycin 1, 2

Symptomatic Management

Antimotility Agents:

• Never give loperamide to children <18 years of age with acute diarrhea 1, 2, 7
• May give loperamide to immunocompetent adults with acute watery diarrhea: 4 mg initial dose, then 2 mg after each unformed stool (maximum 16 mg/day) 2, 7
• Avoid loperamide in inflammatory diarrhea, bloody diarrhea, or diarrhea with fever at any age due to risk of toxic megacolon 1, 2

Antiemetics:

• Ondansetron may be given to children >4 years and adolescents with vomiting to facilitate oral rehydration tolerance 1, 2

Adjunctive Therapies:

• Probiotic preparations may be offered to reduce symptom severity and duration in immunocompetent patients 1, 2
• Zinc supplementation (for children 6 months to 5 years in countries with high zinc deficiency prevalence or signs of malnutrition) reduces diarrhea duration 1, 2

Critical Pitfalls to Avoid

Do not delay rehydration while waiting for diagnostic tests. 2 The primary cause of mortality in viral gastroenteritis is dehydration, not the viral infection itself. 3

Do not give antibiotics for suspected STEC O157 infections, as they increase risk of hemolytic uremic syndrome. 1, 2 Avoid antimicrobials for any STEC producing Shiga toxin 2. 1

Do not use antimotility agents in children or in patients with bloody diarrhea, as this can lead to serious complications including toxic megacolon. 1, 2, 7

Do not treat asymptomatic contacts of patients with diarrhea, but advise them to follow appropriate infection prevention measures including hand hygiene. 1, 2

Monitoring and Follow-up

Continue monitoring hydration status until symptoms resolve. 2 Once rehydrated, administer maintenance fluids and replace ongoing stool losses with ORS until diarrhea and vomiting resolve. 1

Reassess if symptoms persist beyond expected course: For symptoms lasting ≥14 days, consider noninfectious conditions including lactose intolerance, inflammatory bowel disease, or irritable bowel syndrome. 1 Reassess fluid and electrolyte balance, nutritional status, and consider whether antimicrobial therapy is appropriate. 1

Modify or discontinue antimicrobial therapy when a specific pathogen is identified from diagnostic testing. 1, 2