Lecture 26 - Hepatitis B virus Flashcards
(28 cards)
why is hepatitis B an important virus in NZ?
because there are populations that are more susceptible to hepatitis B
where does hepatitis B infect?
liver
what are some common bacterial infections of the liver?
cholecystitis, cholangitis, liver abscess
what are some common viral infections of the liver?
Hepatitis B and C
where do bacterial infections of the liver arise from vs viral infections of the liver?
bacterial infections usually effect the biliary system in one region of the liver and arise from the gut
viral infections usually effects the liver cells diffusely (whole liver) and arise from the bloodstream
which hepatitis virus has a different source of infection from the others and what is it?
hepatitis A, source of infection is the feaces
transmission, mortality rate, risk of chronic infection and vaccine for hepatitis A?
transmission is via the fecal oral route
mortality rate is almost none
risk of chronic infection is nil
there is a vaccine
transmission, mortality rate, risk of chronic infection and vaccine for hepatitis B?
transmission by contact with blood, sexual fluids and sometimes form mother to child
5-10% mortality rate of acute infection (neonates)
variable risk of chronic infection
vaccine yes
transmission, mortality rate, risk of chronic infection and vaccine for hepatitis c?
transmission by contact with blood, sexual fluids, and drug use (needles)
almost no one dies from acute infection
70% chance of chronic infection
no vaccine
what percentage of maori students vs european students were found to have HBV in 1985?
10% of Maori students
0.5% of european students
why do maori, pacific and chinese people have higher rates of HBV infection?
because there were higher rates of hepatitis B in mothers from those areas many years ago, and people from africa which moved up towards europe had no hepatitis B
how do you diagnose HBV?
by detecting the hepatitis B surface antigen (HBsAg) in blood
describe the structure of the hepatitis B virus
outer envelope containing HBsAg
Nucleocapsid containing HBcAg (core antigen)
DNA inside the nucleocapsid
why do we use HBsAg to diagnose HBV infections?
because the liver infected with HBV over produces the HBsAg and is released into the blood as tubules or spheres without viral DNA
- so there is a lot of it and it is cheap and easy to diagnose this way
why are some people who are HBsAg+ more infectious than others?
the more circulating HBsAg, the more infectious, and the higher risk of transmission to child and sexual partners
how can we tell if someone with HBV is highly infectious?
HBeAg presence in blood
what is the risk of transmission when someone is HBsAg+ but HBeAg- ?
10% risk during birth
3% needlestick
what is the risk of transmission when someone is HBsAg+ and HBeAg+ ?
90% at birth
30% with needlestick
how is HBV different to every other virus in terms of entry and infection?
it does absolutely no damage to the liver at all
what causes the damage to the liver in an infection with HBV?
cytotoxic T cells killing virally infected cells
- cause cell damage, inflammation and illness
describe the course of infection which is NOT from birth
number of infected liver cells slowly goes up over three months, then cytotoxic lymphocytes start killing them and so person gets sick, but then the infected liver cells decrease and the person has eradicated the HBV and HBsAb (antibody) levels increase reapidly
- in serious cases someone can die from liver failure
true or false, hepatitis B often leads to re-infection if exposed again
false, once HBsAb produced, you’ll never get it again
describe the course of infection of HBV from birth
baby’s developing immune system doesn’t entirely recognise the HBV virally infected cells, and produces a minimal T cell response which is prolonged for life, never fully eradicating the virus, which gradually scars the liver and can cause cirrhosis or liver cancer after 50-60 years
how can we ensure a baby is born without HBV?
- purify HBsAg from serum of patients who have recovered from HBV
- vaccinate people multiple times with HBsAg so they produce lots of ABs then isolate them
- then give to the baby to coat the surface of virus and prevent it attaching to liver cells
- then vaccinate baby so it doesn’t get infected in future
