Rotavirus Antigen

Overview

Rotavirus is a non-enveloped, double-stranded RNA virus belonging to the Reoviridae family. Under the electron microscope, it appears wheel-like, giving it the name “Rota” (wheel). It is the most common cause of infectious diarrhea in children worldwide, especially in those under five years of age.

The Rotavirus Antigen Test is designed to detect the presence of rotavirus in stool samples, confirming infection. Nearly every child experiences at least one rotavirus infection by age five. Although subsequent infections occur, immunity develops gradually, reducing the severity of later episodes.

Rotavirus primarily infects the small intestine villi, causing villous atrophy. It produces NSP4 protein, which acts as a viral enterotoxin stimulating fluid secretion, leading to watery diarrhea. The infection reduces sodium, glucose, and water absorption and decreases intestinal enzyme activity, resulting in isotonic diarrhea.

Symptoms

Rotavirus antigen positivity is associated with viral gastroenteritis, which manifests as:

1. Gastrointestinal symptoms:
   1. Severe, watery diarrhea (often non-bloody)
   2. Vomiting and nausea
   3. Abdominal cramps and bloating
2. Systemic symptoms:
   1. Fever
   2. Dehydration signs such as dry mouth, sunken eyes, decreased urination, and excessive thirst
   3. Fatigue, weakness, and irritability in children

Severe cases can cause life-threatening dehydration, especially in infants and young children. Adults may also be infected but usually experience milder symptoms.

Causes

Rotavirus antigen presence in stool indicates an active infection, caused by:

1. Fecal-Oral Transmission:
   1. Contaminated food and water
   2. Poor hand hygiene and sanitation
   3. Person-to-person contact
2. Environmental Stability:
   1. The virus is highly stable and can remain viable for weeks to months if not disinfected.
3. Viral Pathophysiology:
   1. Infection of intestinal villi with viral replication in epithelial cells.
   2. NSP4 enterotoxin stimulates fluid secretion, causing watery diarrhea.
   3. Loss of intestinal enzymes (lactase, alkaline phosphatase, sucrase) exacerbates malabsorption and diarrhea.

Risk Factors

Certain groups are more vulnerable to rotavirus infection and antigen positivity:

1. Infants and Children Under 5:
   1. This group experiences the most severe disease, with high hospitalization rates.
2. Unvaccinated Children:
   1. Lack of vaccination increases susceptibility to severe infection.
3. Geographical and Seasonal Factors:
   1. Global distribution with seasonal peaks, especially in winter months.
4. Poor Sanitation and Hygiene:
   1. Communities with limited access to clean water and proper sanitation are at greater risk.
5. Close Contact Settings:
   1. Daycare centers, nurseries, and pediatric wards increase chances of outbreaks.
6. Immunocompromised Individuals:
   1. Patients with weakened immune systems may suffer from prolonged or severe infections.
7. Adults in Contact with Infected Children:
   1. Parents, caregivers, and healthcare workers are at risk, though illness is often milder.

Prevention

Rotavirus infection cannot be entirely avoided, but the spread and severity can be significantly reduced through preventive strategies:

1. Vaccination:
   1. Rotarix (monovalent, 2 doses) and RotaTeq (pentavalent, 3 doses) are effective vaccines integrated into immunization programs.
   2. Vaccination provides strong protection against severe diarrhea and hospitalization.
2. Breastfeeding:
   1. Provides protective maternal antibodies that reduce severity of infection in infants.
3. Sanitation and Hygiene:
   1. Regular handwashing with soap and water.
   2. Safe disposal of diapers and proper sanitation of living spaces.
   3. Disinfection of contaminated surfaces and objects, as the virus can survive for weeks.
4. Sample Collection and Testing:
   1. Stool samples (up to 5 g) should be collected in sterile containers.
   2. Stability: ambient (2 hours), refrigerated (72 hours), frozen (1 week).
   3. Transport samples under refrigeration (2–8°C) with ice packs for accurate results.
5. Public Health Measures:
   1. Community education about hand hygiene, safe water, and proper food handling.
   2. Early medical care for children with diarrhea to prevent dehydration.