Gastroenteritis viruses (norovirus, rotavirus)

Gastroenteritis Viruses - The Diarrhea Duo

⭐ Rotavirus vaccine (live attenuated) can ↑ risk of intussusception.

Norovirus - Cruise Ship Calamity

• Virus: Caliciviridae family; non-enveloped, linear +ssRNA genome.
• Transmission: Fecal-oral route. Highly contagious via contaminated food/water, fomites, or aerosolized vomit. Outbreaks common in crowded settings (📌 NO-ROom on a cruise ship: NOrovirus).
• Clinical: Acute-onset vomiting ("winter vomiting bug"), watery non-bloody diarrhea, abdominal cramps. Self-limiting, resolves in 24-72 hours.
• Diagnosis: Typically clinical. Stool RT-PCR for outbreak confirmation.
• Treatment: Supportive care (oral rehydration). No vaccine available.

⭐ High-Yield: Extremely low infectious dose (<100 viral particles) and prolonged asymptomatic shedding contribute to rapid, widespread outbreaks.

Rotavirus - Diaper Duty Disaster

• Virus: Reoviridae family; non-enveloped, segmented (11) dsRNA virus. Wheel-like appearance.
• Transmission: Fecal-oral. Common in infants & young children (< 5 yrs), especially in daycare.
• Pathogenesis: Infects and destroys mature enterocytes in the small intestine → villous blunting and atrophy → malabsorption.
  • NSP4 Enterotoxin: Key virulence factor. ↑ intracellular calcium → secretory diarrhea.
• Clinical: Acute, profuse, watery, non-bloody diarrhea; vomiting & fever. Dehydration is the main complication.
• Prevention: Live-attenuated oral vaccine is routine for infants.

⭐ The original rotavirus vaccine (Rotashield) was withdrawn due to an increased risk of intussusception.

📌 Reovirus, Oral route, Toddlers, Atrophy of villi.

Clinical Management - Rehydrate & Resolve

• Primary Goal: Supportive care focused on preventing and treating dehydration. The illness is typically self-limiting.
• Rehydration Therapy: Cornerstone of management.
  • Oral Rehydration Salts (ORS): Preferred route for mild to moderate dehydration. Administer small, frequent volumes.
  • IV Fluids (Isotonic): Use for severe dehydration, shock, or when oral intake is impossible (e.g., persistent vomiting). Use Lactated Ringer's or Normal Saline.
• Diet:
  • Continue age-appropriate diet as tolerated. Early re-feeding is encouraged.
  • Avoid high-sugar drinks, fruit juices, and sodas which can worsen osmotic diarrhea.
• Pharmacotherapy (Limited Role):
  • Antivirals: Not available or indicated.
  • Antidiarrheals (e.g., Loperamide): Generally avoided, especially in children, due to risk of toxic megacolon and ileus.
  • Antiemetics (e.g., Ondansetron): May be considered in select cases to facilitate oral rehydration.

⭐ WHO Oral Rehydration Solution: The low-osmolarity WHO formula (75 mEq/L sodium, 75 mmol/L glucose) is key. The 1:1 glucose-to-sodium ratio is critical for co-transport via the SGLT1 transporter in the small intestine, promoting water absorption.

High‑Yield Points - ⚡ Biggest Takeaways

• Norovirus is the leading cause of adult gastroenteritis outbreaks, especially in crowded settings (e.g., cruise ships).
• Rotavirus is the most common cause of severe, dehydrating diarrhea in infants and unvaccinated children.
• Rotavirus features a segmented, dsRNA genome and causes villous blunting in the duodenum, leading to malabsorptive diarrhea.
• The live attenuated rotavirus vaccine carries a small risk of intussusception.
• Transmission for both is primarily fecal-oral.