RNA Viruses

Question 1

Caliciviruses

Answer 1

Caliciviruses are single-stranded positive-sense RNA, non-enveloped, spherical particles.

Norovius

Norovirus replicates in the GI tract and is shed in the stool.

Infection by the Norovirus is by fecal–oral route, person-to-person contact, or by contact with contaminated surfaces.

Norovirus is a major cause of epidemic acute gastroenteritis, particularly at closed environments.

It affects primarily adults and school-age children but not infants.

The clinical presentation is characterized by nausea, vomiting, and diarrhea.

Symptoms last 24 to 48 hours, and the disease is self-limited.

No specific antiviral treatment is available.

Careful attention to hand washing and measures to prevent contamination of food and water supplies should reduce the incidence of these infections.

Hepatitis E virus

Question 2

Dengue virus

Answer 2

• Dengue is commonest arbovirus

• First infection ranges from asymptomatic to severe febrile illness
– lasts 1-5 days
– Improves 3-4 days after rash
– Supportive treatment only

• Re-infection with different serotype
– Antibody dependent enhancement
• Dengue haemorrhagic fever
• Dengue shock syndrome

Question 3

Influenza A

Answer 3

Spherical, enveloped RNA virus

Spread via respiratory droplets- therefore importance of isolation

Can be subtyped depending on the antigen associated with its outer viral proteins:

Haemagglutinin (H) Neuraminidase (N)

So far 16 H antigen and 9N antigen subtypes have been identified.