Hepatitis Viruses
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Direct answer
Five main viruses cause viral hepatitis: hepatitis A and E, spread faecal–orally and causing self-limiting acute illness, and hepatitis B, C and D, spread by blood and body fluids with a propensity to chronicity, cirrhosis and hepatocellular carcinoma. Hepatitis B, a deoxyribonucleic acid hepadnavirus, is tracked by its serological markers — surface antigen, e antigen and core antibody — while hepatitis C, a flavivirus, is diagnosed by antibody confirmed by ribonucleic acid testing and is now curable with direct-acting antivirals. Hepatitis D is a defective virus needing hepatitis B, and hepatitis E is dangerous in pregnancy.
What you must remember
- Hepatitis A: a picornavirus spread faecal–orally; immunoglobulin M antibody marks current infection and immunoglobulin G past infection; a killed vaccine exists; it never becomes chronic.
- Hepatitis B: a partially double-stranded circular deoxyribonucleic acid hepadnavirus transmitted by blood, sex and from mother to baby at birth; most neonatal infections become chronic while most adult infections clear.
- Hepatitis B markers: surface antigen is the first and main marker, e antigen indicates active replication and high infectivity, core antigen is intracellular and unmeasured in serum, immunoglobulin M core antibody marks acute infection and fills the window period, surface antibody means recovery or vaccination, and viral deoxyribonucleic acid quantifies load.
- Hepatitis B prevention: the recombinant surface-antigen vaccine in three doses, with birth-dose vaccine and immunoglobulin for infants of infected mothers preventing most perinatal transmission.
- Hepatitis C: a flavivirus, mainly blood-borne, strongly tending to chronicity; direct-acting antivirals cure the large majority; no vaccine exists.
- Hepatitis D: a defective circular ribonucleic acid virus using the hepatitis B surface antigen as its coat, so it infects only hepatitis B carriers, making disease severer; hepatitis B vaccination protects against it.
- Hepatitis E: enterically transmitted and waterborne; fulminant hepatic failure with high maternal mortality complicates third-trimester infection.
Common confusion
The marker pairs of hepatitis B are mixed up — surface antigen with surface antibody for infection versus immunity — and only the core antibody, not the core antigen, is measured in serum. The window period, after surface antigen disappears and before surface antibody appears, is bridged by immunoglobulin M core antibody. Remember that immunoglobulin M against hepatitis A and E diagnoses acute disease, and that the hepatitis B surface-antigen-positive mother needs her baby immunised at birth.
Exam-focused takeaway
In theory, write the viruses in a fixed order with nucleic acid type, transmission, incubation, chronicity and prevention; the hepatitis B marker timeline deserves a labelled diagram. In viva, expect interpretation of a given serological profile, why hepatitis E kills pregnant women, and why hepatitis D cannot exist alone. At the practical, interpreting hepatitis B serology reports is a standard question.
Frequently asked questions
Which hepatitis viruses spread faecal–orally?
Hepatitis A and E through contaminated water and food; hepatitis B, C and D spread through blood and body fluids and share a tendency to chronic disease.
Which marker appears first in hepatitis B?
The surface antigen, weeks before symptoms; immunoglobulin M core antibody is the acute-phase marker that fills the window period.
What does e antigen indicate?
Active viral replication and high infectivity; its loss with appearance of e antibody marks seroconversion towards remission.
How is hepatitis C diagnosed and treated?
Antibody screening confirmed by ribonucleic acid testing; direct-acting antiviral tablets cure the large majority.
Why is hepatitis D called defective?
It borrows the hepatitis B surface antigen as its coat, so it replicates only alongside hepatitis B; vaccinating against B prevents D.
Why is hepatitis E dangerous in pregnancy?
Third-trimester infection can precipitate fulminant hepatic failure with high maternal and fetal mortality, so pregnant women with jaundice in an outbreak need urgent care.