Rotavirus and Viral Gastroenteritis
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Direct answer
Rotavirus is a non-enveloped double-stranded RNA virus with 11 genome segments, and it is the commonest cause of severe diarrhoea in infants and young children worldwide. It infects mature enterocytes at the villous tips, causing malabsorption and secretory diarrhoea. Norovirus, a positive-sense RNA calicivirus, is the commonest cause of gastroenteritis outbreaks in people of all ages, including adults.
What you must remember
- Structure: Rotavirus has a triple-layered icosahedral capsid, and its outer proteins VP7 and VP4 are the neutralising antigens that define the G and P genotypes.
- Groups: Rotavirus groups A to G are defined by the inner capsid protein VP6, and group A causes most severe disease in young children.
- Pathogenesis: Infection of mature enterocytes causes villous atrophy and malabsorption, and the viral protein NSP4 acts as an enterotoxin that produces secretory diarrhoea.
- Diagnosis: Stool ELISA or latex agglutination detects viral antigen, RT-PCR confirms the result, and the 11-band polyacrylamide gel pattern was historically used to identify strains.
- Norovirus: A non-enveloped positive-sense ssRNA calicivirus with a short incubation period, causing vomiting-predominant outbreaks in cruise ships, care homes and among food handlers.
- Management: Oral rehydration is the mainstay, with zinc supplementation for 10 to 14 days in children under IMNCI guidance, and antibiotics are not indicated for viral causes.
- Vaccines: Live oral rotavirus vaccines, including the indigenous Rotavac, are part of India's universal immunisation programme.
- Safety: Intussusception is a rare complication after rotavirus vaccination, most often in the first days after the first dose.
Rotavirus and norovirus side by side
Rotavirus and norovirus cause similar illness, so exams separate them by genome, age group and laboratory test. The table sets out the features that most often discriminate between them.
| Feature | Rotavirus | Norovirus |
|---|---|---|
| Genome | dsRNA, 11 segments | Positive-sense ssRNA |
| Typical patients | Infants and young children | All ages, outbreaks in adults |
| Incubation | About 1 to 3 days | About 12 to 48 hours |
| Routine diagnosis | Stool antigen ELISA or RT-PCR | RT-PCR |
| Vaccine | Licensed live oral vaccines | None licensed |
Rotavirus can be grown in cell culture with trypsin, whereas human norovirus is not routinely cultivated, which is why diagnosis depends on molecular methods. The age pattern and outbreak setting are often enough to suggest the cause before a test returns.
Clinically, the first task is to assess dehydration, because its degree decides between oral rehydration salts and intravenous fluids. Stool culture for bacteria is reserved for patients with blood in stool, high fever or a pattern that does not fit a viral illness.
Where the exam tries to catch you
Gastroenteritis questions usually turn on the genome, the age group and the treatment mistakes students make.
- Trap: Calling norovirus a dsRNA virus like rotavirus Correct: Norovirus is a non-enveloped positive-sense ssRNA calicivirus, so genome type is the cleanest way to separate it from rotavirus.
- Trap: Assuming rotavirus causes mainly adult outbreaks Correct: Rotavirus primarily affects infants and young children, whereas norovirus outbreaks are common in adults on cruise ships, in care homes and among food handlers.
- Trap: Giving antibiotics as the main treatment for viral diarrhoea Correct: Rehydration and zinc are the mainstays of care, since antibiotics do not act on viruses and are not routinely indicated.
Frequently asked questions
Which genome feature distinguishes rotavirus from norovirus?
Rotavirus has a double-stranded RNA genome in 11 segments within an icosahedral triple-layered capsid, whereas norovirus has a single-stranded positive-sense RNA genome. This genome difference is a classic exam discriminator between the two.
Why does rotavirus cause severe diarrhoea mainly in infants?
Infants and young children are highly susceptible to rotavirus because they have little prior immunity to it. Repeated infections in childhood produce protective immunity, so rotavirus disease in older children and adults is generally milder.
Which test confirms rotavirus infection in a child with diarrhoea?
Rotavirus is confirmed by detecting viral antigen in stool using ELISA or latex agglutination, with RT-PCR used for confirmation. Bacterial culture does not detect the virus, so it cannot confirm rotavirus infection.
Why is zinc given with oral rehydration in childhood diarrhoea?
Zinc supplementation reduces the duration and severity of diarrhoea in children, and it is part of standard management under IMNCI. It is given alongside oral rehydration salts, which correct dehydration, because antibiotics are not required for viral causes.
What is a rare complication of rotavirus vaccination?
Intussusception is a rare complication of rotavirus vaccination, most often in the first days after the first dose. Surveillance for it forms part of vaccine safety monitoring, and it is why vaccine doses are timed with care.