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Hepatitis B (HBV) (Genotypes (Alaskan Natives (Homogeneous discrete…
Hepatitis B (HBV)
Clinical Features
Incubation Period
60-90 day average
45-180 day range
Acute Case Fatality Rate
0.5-1%
Clinical Illness (Symptoms)
Increases with age >5yrs: 30-50%
Chronic Infection
Age decreases the chance of getting a chronic infection
<5yrs, 30-90%
Premature Mortality from Chronic Liver Disease
15-25%
Due to Liver cirrhosis OR hepatocellular carcinoma (tumour)
Epidemiology
Impact
Globally
2 billion ever infected
240mil wit h chronic
780,000 deaths per year
USA
5% of total population ever infected
2000 deaths per year
Chronic
Highest prevalence in Africa and SE Asia
Lowest in America
Virus Particle
Enveloped Viruss
Partially dsDNA genome
Antigens
HBs Ag
Marker indicates chronic infection
HBc Ag
Core antigen
Represents non-enveloped particles (current virus no.)
HBe Ag
Procccessed from pre-C protein
Marker for active infection
Anitgens to HBs
Invovled in virus clearance
Indicates virus has been cleared
Antigens to HBe
(+) Then the virus is still replicating
Not much means quiescent form of infection
Serological Time Course
Acute
Anti-HBs
HBs Ag not as easily recognised
Peaks ~36 weeks
Well after peak in viremia
Indicates virus clearance and recovery
Viremia
Peaks ~ 8 weeks
Before IgM peak
Symptoms
If you have symptoms clearance is more likely
Same time as
HBe/Anti-HBe
Get anti-HBe around same time as IgM peak
Can indicate a more quiescent infection
IgM/Anti-HBc
Peak is after peak viremia
~16weeks
Chronic
Symptoms
Asymptomatic up to 6 months
IgM/Anti-Hbc
Peaks ~16 weeks
Doesn't eliminate infection
Anti-HBs
None
HBs Antigen levels reach a plateau
Anti-HBe
May take years for antibodies to switch to this
Indicates a quiescent infection
Transmission
Sexual
Parenteral
Perinatal
High
Blood
Serum
Moderate
Semen
Vaginal Fluid
Saliva
Low
Urine
Faeces
Sweat
Tears
Genotypes
Has genotypes A-H
Isolates are clustered depending on animal
As more isolates sequenced get and increase in diversity
Has a heterogeneous distribution
Shows the virus has been around for a long time
Has since diverged
Alaskan Natives
Homogeneous discrete genomes
Results suggested genotype defines infection outcome
The greater the age of clearance the more likely to get end stage liver cancer
Location of genotypes represents migration
Sub genotypes too
B clears quickly
C appears not to interact with E
Host Variation
Various HLA loci
Host antigen presentation will be different
Inteferon gamma and TNF alpha indicate an active immune response