Viral Hepatitis

Viral hepatitis is inflammation of the liver caused by one of five distinct viruses — labelled A through E — that share a target organ but almost nothing else. They differ in how they spread, whether they cause lifelong infection, and how much long-term harm they do. Understanding hepatitis well means holding two ideas at once: the acute illness at the bedside, with its jaundice, dark urine, and malaise, and the silent, decades-long process by which some of these viruses scar the liver toward cirrhosis and cancer.

This topic matters enormously. Hepatitis B and C together infect hundreds of millions of people worldwide and are leading causes of liver cirrhosis and hepatocellular carcinoma. Yet hepatitis A and B are vaccine-preventable, and hepatitis C is now curable in most patients with a short course of oral tablets. Few areas of medicine reward accurate reasoning so directly: get the serology right, and you can tell a frightened patient whether they will clear the virus, need lifelong monitoring, or can be cured outright.

Learning Objectives

• Distinguish the five hepatitis viruses by transmission, incubation, and chronicity.
• Interpret hepatitis B serology (HBsAg, anti-HBs, anti-HBc, HBeAg) to stage infection.
• Explain why hepatitis C so often becomes chronic and how it is now cured.
• Recognise acute liver failure and the complications of chronic hepatitis.
• Apply prevention strategies: vaccination, screening, and post-exposure prophylaxis.
• Understand the special danger of hepatitis D co-infection and hepatitis E in pregnancy.

Quick Answer

Viral hepatitis is liver inflammation caused by hepatitis viruses A, B, C, D, and E. A and E spread by the faecal-oral route (contaminated food and water) and cause acute, self-limiting illness — though E is dangerous in pregnancy. B, C, and D spread through blood and body fluids and can become chronic, silently damaging the liver over decades toward cirrhosis and liver cancer. Diagnosis relies on serology and viral nucleic acid tests: hepatitis B is staged with a panel of antigens and antibodies, while hepatitis C is confirmed by detecting viral RNA. Hepatitis A and B are prevented by safe, effective vaccines; hepatitis D only infects those who already carry B. The landmark modern advance is that hepatitis C is now cured in over 95 percent of patients with 8 to 12 weeks of oral direct-acting antivirals, while hepatitis B is controlled — not usually cured — with long-term suppressive therapy.

Where It Came From

For most of medical history, jaundice was a single mysterious symptom. During the twentieth century's wars, doctors noticed two epidemiological patterns: an "infectious hepatitis" that spread through camps like a gut infection, and a "serum hepatitis" that followed blood transfusions and vaccination with pooled human serum. This clinical clue — one spread by contact, one by blood — foreshadowed the viruses we now call A and B.

The breakthrough came in 1965 when Baruch Blumberg, studying blood proteins, stumbled on the "Australia antigen" in the serum of an Aboriginal Australian. It turned out to be the surface coat of the hepatitis B virus, and its discovery let doctors screen blood donors and later build the first hepatitis B vaccine — the first vaccine ever shown to prevent a human cancer. Blumberg won the Nobel Prize in 1976. Hepatitis A virus was identified in 1973. But a stubborn "non-A, non-B" hepatitis kept appearing after transfusions. It took until 1989, using then-novel molecular cloning, for Michael Houghton, Harvey Alter, and colleagues to identify the hepatitis C virus — work that earned the 2020 Nobel Prize. The motivation throughout was intensely practical: to make the blood supply safe and to stop a hidden epidemic of cirrhosis and liver cancer that surgeons and hepatologists were seeing without knowing its cause.

The Five Viruses: A Field Guide

The single most useful mental model is to split the viruses by how they spread, because route predicts chronicity.

The faecal-oral pair (A and E). Hepatitis A (a picornavirus) and hepatitis E (a hepevirus) spread through contaminated food and water. Both cause acute, self-limiting hepatitis and do not establish chronic infection in healthy people. Hepatitis A is common wherever sanitation is poor and is a classic traveller's infection; children often have mild or silent disease while adults get sicker. Hepatitis E is the world's most common cause of acute viral hepatitis and carries a frightening feature: in pregnant women, particularly in the third trimester, it can cause fulminant liver failure with mortality up to 20 to 25 percent.

The blood-borne group (B, C, and D). These spread through blood, sexual contact, and from mother to child. Hepatitis B (a DNA virus, hepadnavirus) can be acute or chronic; the risk of chronicity depends dramatically on age at infection — over 90 percent of infected newborns become chronic carriers, versus under 5 percent of infected adults. Hepatitis C (an RNA flavivirus) is the opposite in its natural history: acute infection is often silent, but roughly 75 to 85 percent of those infected fail to clear it and become chronic. Hepatitis D (the delta agent) is a defective virus that cannot replicate on its own — it borrows hepatitis B's surface coat, so it only infects people who also have hepatitis B, and when it does, the disease is more severe.

Worked example: reading a hepatitis B panel

A 34-year-old man from an endemic region is screened before starting immunosuppressive therapy. Results: HBsAg positive, anti-HBc positive (IgG), HBeAg positive, HBV DNA high, anti-HBs negative. Read it step by step:

• HBsAg positive means active infection — the virus's surface protein is circulating.
• Anti-HBc IgG positive with negative IgM means the infection is not recent; this is established, chronic infection rather than an acute attack.
• HBeAg positive with high DNA signals high replication and high infectivity.
• Anti-HBs negative means he has not developed protective, neutralising antibody.

Conclusion: chronic hepatitis B in the immune-active phase. He needs antiviral therapy (e.g. tenofovir or entecavir) before and during immunosuppression to prevent a dangerous reactivation flare. Contrast this with someone who is HBsAg negative, anti-HBs positive, anti-HBc negative — that pattern means vaccinated and immune, never infected.

Acute Illness Versus the Silent Chronic Course

Acute viral hepatitis often follows a recognisable arc. A prodrome of fatigue, nausea, anorexia, and a distaste for cigarettes or fatty food precedes the icteric phase, when bilirubin rises: the patient notices dark, tea-coloured urine, then pale stools, then yellowing of the sclera and skin. The liver may be tender. Blood tests show markedly raised transaminases (ALT and AST often in the thousands), with bilirubin elevated and, in severe cases, a rising INR signalling impaired synthetic function. Most acute cases recover fully.

The feared exception is acute liver failure (fulminant hepatitis): jaundice plus coagulopathy plus encephalopathy (confusion progressing to coma) developing within weeks. This is a medical emergency requiring specialist care and sometimes urgent liver transplantation.

Chronic hepatitis B and C are far quieter and, precisely because they are silent, far more dangerous at a population level. Over years to decades, ongoing inflammation drives fibrosis, then cirrhosis. Cirrhosis brings portal hypertension (varices, ascites), synthetic failure, and a yearly risk of hepatocellular carcinoma. Hepatitis B is unusual in that it can cause liver cancer even without cirrhosis, because the virus integrates into host DNA — which is why HBsAg-positive patients need cancer surveillance with ultrasound regardless of fibrosis stage.

Diagnosis and Treatment

Diagnosis combines serology (antigens and antibodies) with molecular tests (viral DNA or RNA) that measure how much virus is present. For hepatitis C, screening is by antibody test, but a positive antibody only means past exposure; confirmation and the decision to treat require detecting HCV RNA, because some people cleared the virus and remain antibody-positive.

Treatment differs sharply by virus:

• Hepatitis A and E: supportive care only; almost all recover. No specific antiviral in routine use.
• Hepatitis B: long-term suppression, not cure, with nucleos(t)ide analogues (tenofovir, entecavir). These drive the virus down and halt progression but rarely eliminate it, because HBV persists as stable cccDNA inside liver cells. Therapy is often lifelong.
• Hepatitis C: the great success story. Oral direct-acting antivirals (DAAs such as sofosbuvir combined with velpatasvir or ledipasvir) taken for 8 to 12 weeks cure over 95 percent of patients, defined as a sustained virologic response — undetectable RNA 12 weeks after finishing. This is a genuine cure.
• Hepatitis D: historically the hardest to treat; pegylated interferon has limited success, and newer agents (bulevirtide) are emerging.

Real-World Applications

• Blood and organ safety: universal donor screening for HBsAg and HCV RNA has made transfusion-transmitted hepatitis rare in resourced settings.
• Antenatal care: screening all pregnant women for HBsAg allows the newborn to receive hepatitis B vaccine plus immunoglobulin at birth, preventing mother-to-child transmission that would otherwise almost always become chronic.
• Needlestick management: a healthcare worker exposed to blood is assessed for hepatitis B (vaccination status guides immunoglobulin) and hepatitis C (monitored, treated if infected).
• Travel medicine: hepatitis A vaccine before travel to endemic regions, and food-and-water precautions against A and E.
• Public health elimination: the WHO targets viral hepatitis elimination by 2030, driven largely by universal infant hepatitis B vaccination and mass hepatitis C treatment programmes.

Common Mistakes

1. Assuming a positive hepatitis C antibody means active infection. It does not — it means exposure. Some people spontaneously cleared the virus. You must check HCV RNA before diagnosing chronic infection or starting treatment. Treating on antibody alone wastes therapy and mislabels a cured patient.

2. Thinking hepatitis B can be readily cured like hepatitis C. They are biologically different. HCV is an RNA virus with no stable reservoir, so DAAs eradicate it. HBV parks its genome as cccDNA in the nucleus, so current drugs suppress but do not clear it. Stopping therapy prematurely can trigger a severe flare.

3. Overlooking hepatitis E in pregnancy. Because hepatitis E is often dismissed as a mild self-limiting infection, its lethal course in pregnant women is missed. A pregnant woman with acute hepatitis and a travel or water-exposure history needs urgent evaluation.

4. Forgetting to check for hepatitis D in a hepatitis B patient who deteriorates. A sudden worsening in a stable HBsAg-positive person can signal delta superinfection.

Comparison and Connections

Feature	Hep A	Hep B	Hep C	Hep D	Hep E
Virus type	RNA	DNA	RNA	Defective RNA	RNA
Main transmission	Faecal-oral	Blood, sexual, perinatal	Blood	Blood (needs HBV)	Faecal-oral
Becomes chronic?	No	Sometimes	Usually	If with HBV	No (rarely in immunosuppressed)
Vaccine available?	Yes	Yes	No	Via HBV vaccine	Limited (one licensed in some countries)
Special danger	—	Cancer without cirrhosis	Silent cirrhosis	Severe co-disease	Fatal in pregnancy
Treatment	Supportive	Long-term suppression	Curable (DAAs)	Difficult	Supportive

Viral hepatitis should be distinguished from other causes of a raised ALT and jaundice: alcoholic and non-alcoholic fatty liver disease, drug-induced injury (paracetamol overdose is the classic cause of acute liver failure in the West), autoimmune hepatitis, and biliary obstruction. The pattern of liver enzymes and the history usually separate them, but serology settles the viral question.

Practice Questions

Recall

Which two hepatitis viruses are transmitted by the faecal-oral route?

Answer: Hepatitis A and hepatitis E.

Understanding

Why does hepatitis C become chronic in most people while hepatitis A never does?

Answer: Hepatitis A causes a brisk, effective immune response and is fully cleared, leaving lasting immunity. Hepatitis C mutates rapidly, generating many variants (quasispecies) that evade the immune response, so in roughly three-quarters of people the virus persists and establishes chronic infection.

Application

A blood donor is found HBsAg negative, anti-HBs positive, anti-HBc negative. What does this pattern mean, and is the donor safe?

Answer: This is the pattern of vaccine-induced immunity: protective surface antibody without evidence of past natural infection (anti-HBc would be positive if they had been infected). The donor is immune and not infectious for hepatitis B.

Analysis

A pregnant woman in her third trimester develops acute jaundice, markedly raised transaminases, and rising confusion after returning from a region with poor sanitation. What is the most concerning diagnosis and why is her risk elevated?

Answer: Fulminant hepatitis E. Hepatitis E acquired via contaminated water carries a strikingly high mortality (up to about 20 to 25 percent) in the third trimester, with acute liver failure — the encephalopathy here is an ominous sign. She needs urgent specialist and obstetric care.

FAQ

Can you have hepatitis and feel completely well? Yes — this is the danger of chronic hepatitis B and C. Many people have no symptoms for years or decades while the virus quietly scars the liver, which is why screening at-risk groups matters.

If hepatitis C is curable, why not just wait to catch it and get treated? Because chronic infection can cause irreversible cirrhosis and liver cancer before you are diagnosed, and cure removes the virus but does not fully undo established scarring. Prevention and early treatment are far better.

Does having hepatitis A protect me from the others? No. Immunity to one hepatitis virus gives no protection against the others — they are unrelated viruses. You can be immune to A yet still catch B, C, or E.

Why is there no hepatitis C vaccine? The virus mutates so rapidly and comes in so many genetic variants that a durable protective vaccine has been very hard to design, though research continues. Fortunately, effective cure has reduced the urgency somewhat.

Can hepatitis B come back after it seems controlled? Yes. In people whose immune system is suppressed — for example by chemotherapy, steroids, or biologic drugs — hepatitis B can reactivate dangerously. This is why patients are screened for HBsAg and anti-HBc before immunosuppression and given prophylactic antiviral cover if needed.

Quick Revision

• Five viruses: A, B, C, D, E. Faecal-oral = A and E; blood-borne = B, C, D.
• A and E: acute, self-limiting; E is deadly in pregnancy.
• B: DNA virus; chronicity depends on age (newborns over 90 percent). Suppressed, not cured; can cause cancer without cirrhosis.
• C: usually becomes chronic; now cured in over 95 percent with 8 to 12 weeks of oral DAAs.
• D (delta): needs hepatitis B to replicate; makes disease worse.
• Vaccines exist for A and B (B vaccine also protects against D).
• Hepatitis C antibody = exposure; confirm active infection with HCV RNA.
• Acute liver failure = jaundice + coagulopathy + encephalopathy = emergency.

Related Topics

Prerequisites

• The Medicine of Infections and How to Treat Them
• Liver structure and function (see ../../2._Physiology/index.md)

Related Topics

• Infective Endocarditis
• Cirrhosis and portal hypertension (see ../../28._Gastroenterology/index.md)
• Vaccination and immunisation (see ../../34._Immunology/index.md)

Next Topics

• Hepatocellular carcinoma and liver cancer surveillance (see ../../32._Oncology/index.md)
• HIV and blood-borne co-infections (see ../../33._Infectious_Diseases/index.md)