Transmission 1 -> Heptatitus example

Question 1

Hep A

Answer 1

Faecal oral

SIR (not chronic)

Two types of dynamic:
- Endemic where prevelance is higher therefore high immunity and eradication is ast.
- > Endemic state less dangerous as individuals infected when young where disease is less severe.
- Epidemic where prevelance is low, with few immune individuals so rapid spread following outbreak.

Infection depends on age:
- <6: 70% of infections are asymptomatic
- >6: More infection are symptoatic with 70% of individuals developing jaundice

Question 1

Hepatitus overall

Answer 1

Hepatitis is a clinical condition that causes inflammation of the liver.

Different viruses from different families cause this condition.

Different modes of transmission.

Varries whether the virus is chronic or not.

Leads to different prevention mechanisms

Bad in pregnant women

Question 2

Hep E

Answer 2

Transferred through blood or exchange of bodily fluids

SIR model

Two main dynamics

Question 3

Hep c

Answer 3

Transferred through blood or exchange of bodily fluids
- Example: Vaccination against schistosomiasis in Egypt lead to the spread of HCV due to unstrelised needles

SI and SIR dyamics as infections can be either chronic or not. -> most individuals are chronic

Evades the immune system:
- Enveloped RNA virus that exhibits high levels of diversity both within the host and between different populations.
- Innate: directly inhibits natural killer cells and dendritic cells that promote adaptive immunity
- Adaptive: Directly and indirectly prevent activation of Killer T cells. HCV mutation creates epitopes that evade recognition, Elicit interferring antibodies.

Question 4

Hep B

Answer 4

Transferred through blood or exchange of bodily fluids

Outcome:
- chronically infects ~ 300 million people world-wide and is responsible for ~ 1 million deaths annually
- Chronic carriers are at a greatly increased risk of developing cirrhosis and hepatocellular carcinoma.

SIR and SI dynamics

Dichotimus disitrbution with regions of high prevalence and low prevalence due to interesting dynamic.

Children:
- Innaparent disease with 95% chronic infections. (SI)
- Infected only when prevelance is high and infected from their mothers.
- > Infants born with Hep B e antigen which induces immune tolerance leading to chronic state.

Adults:
- 1-8% chronic infection and 20% accute infection. (SIR)

feedback mechanism leads to dichotamous dynamics:

Per capita risk of infection (Lambda) -> age of infection (A) -> Number of chronic infections (f) -> Prevalence of disease.

Get +ve feedback: more infection -> more likely infected when young -> more likely a carrier -> Increased transmission rate

Low R0, but Hep B can be maintained if prevelance is high enough leading to children being infected and becoming chronic carriers.

Question 5

Overall

Answer 5

Hep A and E: SIR
Hep B and C: SIR and SI

Hep B is especially interesting with feeback loop