Paper I — 2022 July (Supplementary) (2019 Scheme) — Q7
4 min read
Paper I
2022 July (Supplementary) (2019 Scheme) · 100 marks · 180 min
Question
What are the differences between Hepatitis A virus and Hepatitis B virus. Describe
various markers of HBV in detail and their applications (3+5)
Q78 marksShort Essays
Answer
Differences between Hepatitis A virus (HAV) and Hepatitis B virus (HBV)
Feature
HAV
HBV
Genome
Picornavirus, single-stranded RNA
Hepadnavirus, partially double-stranded DNA
Transmission
Faeco-oral
Parenteral, sexual, vertical
Chronicity
Never causes chronic infection
Can cause chronic infection (>6 months)
Carrier state
None
Present
Long-term complications
None (self-limiting)
Cirrhosis, hepatocellular carcinoma
Vaccine type
Inactivated whole-virus
Recombinant subunit (HBsAg)
Diagnosis
IgM anti-HAV (acute infection)
Multiple serological markers (see below)
Markers of HBV and their applications
HBsAg — first marker to appear; indicates current infection (acute or chronic if >6 months); screening test; basis of the vaccine.
Anti-HBs — indicates recovery with immunity, or successful vaccination.
IgM anti-HBc — indicates recent/acute infection; the only detectable marker during the window period (when HBsAg has cleared but anti-HBs has not yet risen).
IgG anti-HBc — persists long-term, indicating past or current infection (absent after vaccination, distinguishing natural infection from vaccine-induced immunity).
HBeAg — marker of active viral replication and high infectivity.
Anti-HBe — appearance generally indicates reduced replication/infectivity (though precore mutants are an exception).
HBV DNA (quantitative PCR) — the most direct marker of active viral replication, used for monitoring disease activity and treatment response in chronic infection.
