0304 - Gastro Viruses

Question 1

Name the major viral causes of adult and paediatric gastroenteritis

Answer 1

Paediatric - Group A Rotavirus

Adult/epidemic - Norovirus

Question 2

Identify similarities across the viruses that cause gastroenteritis

Answer 2

Similarities
Small and tough, non-enveloped, resistant to drying and hard to disinfect
Rapid disease course - incubation 24 hours, symptoms 24 hours to 7 days
Spectacular replication - low minimal infectious dose (<10), massive yield, up to 10^10 per mL

Question 3

Identify differences across the viruses that cause gastroenteritis

Answer 3

Rotavirus - Paediatric diarrhoea, Norovirus - Epidemic Gastro
Rotavirus DS, norovirus SS,
Rotavirus and Norovirus - RNA, Adenovirus - DNA

Question 4

What is the pathogenesis and likely course of rotavirus disease?

Answer 4

Pathogenesis - direct viral damage to enterocytes at tip of villi leads to shortening of villi, malabsorption and secretion.
Course - 3 days of vomiting, overlapped by 5 days of diarrhoea.

Question 5

explain the basis of the rotavirus vaccine in terms of molecular biology and immunology

Answer 5

Live, attenuated virus. Rotavirus has 2 surface proteins (P and G), and the virus contains one or both of these genes on a ‘backbone’ virus (e.g. Bovine rotavirus WC3). Different G/P combinations (gene segments) allow protection against different strands, and bovine virus ensures that it doesn’t infect humans.

Question 6

Noting the risk of intussusception, why is rotavirus vaccination a good public health measure?

Answer 6

Rotavirus vaccine has a small increased risk of intussusception (15 cases added to 200), while reducing hospitalisations and ED visits by 70%, as well as significantly reducing deaths in the developing world.

Question 7

Describe the way human volunteers shape our understanding of viruses that cannot be grown in vitro, with reference to noroviruses

Answer 7

Need to provide a living host for the virus. In viruses that are cleared quickly (e.g. norovirus), the virus is cleared before IgG can be produced. Thus, volunteers are required to knowingly ingest the virus (from purified poo), to keep it alive until antigens can be made, so the virus can be more readily identified for study. Otherwise almost impossible to find it in the sample (without knowing what you’re looking for).