Infectious Disease and Microbiology - Viral Hepatitis

Basics

Description

Viral hepatitis refers to inflammation and injury of the liver caused by hepatotropic viruses, particularly hepatitis A, B, C, D, and E viruses.

Disease may be:

• Acute and self-limited
• Chronic and progressive
• Fulminant, with massive hepatic necrosis and acute liver failure

The likelihood of chronic infection varies greatly by virus. HAV and HEV usually cause acute disease only, whereas HBV, HCV, and HDV may cause chronic infection.

Fulminant hepatitis is characterized by severe hepatic necrosis with rapid development of liver failure, coagulopathy, and encephalopathy.

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Major Hepatitis Viruses

The principal hepatotropic viruses are:

• Hepatitis A virus (HAV)
• Hepatitis B virus (HBV)
• Hepatitis C virus (HCV)
• Hepatitis D virus (HDV)
• Hepatitis E virus (HEV)

Hepatitis G virus has historically been described, but it is not considered a major cause of clinically significant chronic hepatitis.

Other viruses that can cause hepatitis include:

• Epstein-Barr virus
• Cytomegalovirus
• Herpes simplex virus
• HIV
• Adenovirus
• Measles virus
• Enteroviruses

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Epidemiology

Hepatitis A

HAV has a worldwide distribution.

Transmission is predominantly:

Fecal-oral

Common sources include:

• Contaminated food
• Contaminated water
• Close household contact
• Outbreaks in congregate settings

Sexual transmission, particularly with oral-anal exposure, may also occur.

Chronic infection does not occur.

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Hepatitis B

HBV remains a major global infection.

Major routes of transmission include:

• Blood exposure
• Sexual transmission
• Injection drug use
• Needlestick exposure
• Perinatal transmission
• Vertical transmission
• Contaminated blood products where screening is inadequate

The probability of chronic infection is strongly related to age at acquisition.

Neonatal or perinatal infection

→ Very high risk of chronicity

Adult-acquired infection

→ Most immunocompetent adults clear the infection spontaneously

This age-dependent difference is one of the most important features of HBV infection.

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Hepatitis C

HCV is predominantly a blood-borne infection.

Important routes include:

• Injection drug use
• Shared injection equipment
• Needlestick injuries
• Unscreened blood transfusion
• Organ transplantation from an infected donor
• Perinatal transmission
• Sexual transmission, although less efficient than with HBV

Without treatment, chronic infection develops in a substantial proportion of infected individuals.

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Hepatitis D

HDV is a defective RNA virus that requires hepatitis B surface antigen (HBsAg) for its life cycle.

Therefore:

No HBV → no HDV infection

HDV occurs in two patterns:

Coinfection

HBV and HDV are acquired at the same time.

Superinfection

HDV infects a person who already has chronic HBV infection.

Superinfection is generally associated with more severe disease and a greater risk of chronic liver injury.

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Hepatitis E

HEV resembles HAV epidemiologically.

Transmission is mainly:

Fecal-oral

Large outbreaks are especially associated with:

• Contaminated water
• Poor sanitation
• Developing regions

Most infections are acute and self-limited, although chronic HEV can occur in selected immunocompromised patients.

HEV deserves special attention during pregnancy because severe disease may occur, particularly later in gestation.

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Risk Factors

Hepatitis A

Important risk factors include:

• Travel to areas with poor sanitation
• Household or close contact with an infected person
• Men who have sex with men
• Drug use
• Homelessness
• Occupational or institutional exposure in selected settings
• Contaminated food or water exposure

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Hepatitis B

Important risk factors include:

• Unprotected sexual contact
• Multiple sexual partners
• Men who have sex with men
• Injection drug use
• Occupational blood exposure
• Hemodialysis
• Household exposure to chronic HBV
• Birth in or immigration from endemic regions
• Perinatal exposure
• Repeated blood-product exposure
• HIV infection

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Hepatitis C

Major risk factors include:

• Injection drug use
• Sharing injection equipment
• Needlestick injury
• Blood transfusion before modern screening
• Hemodialysis
• HIV infection
• Tattoos or piercings performed with inadequately sterilized equipment
• Organ transplantation from an infected donor

Intranasal drug use may also pose risk when blood-contaminated equipment is shared.

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Hepatitis D

Risk factors are essentially those of HBV because HDV depends on HBV infection.

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Hepatitis E

Risk factors resemble HAV and include:

• Contaminated water
• Poor sanitation
• Travel to endemic areas

Zoonotic transmission can also occur in some regions.

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Prevention

Hepatitis A Prevention

The most important strategies are:

• Handwashing
• Safe food handling
• Clean water
• Improved sanitation
• Vaccination

HAV vaccine is highly effective and is routinely used in many countries.

It is particularly important for:

• Travelers to endemic regions
• People with chronic liver disease
• Men who have sex with men
• People who use drugs
• Certain occupational or outbreak settings

Post-exposure prophylaxis may involve:

• HAV vaccination
• Immune globulin in selected high-risk individuals

The exact choice depends on age, immune status, liver disease, and timing of exposure.

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Hepatitis B Prevention

HBV vaccination is one of the most effective preventive measures in infectious disease.

Vaccination is recommended broadly, including routine infant vaccination and vaccination of nonimmune adults.

Particularly important groups include:

• Healthcare workers
• Hemodialysis patients
• Injection drug users
• Sexual contacts of infected persons
• People with multiple sexual partners
• Travelers to endemic areas
• Household contacts of chronic HBV carriers

After a significant exposure in a nonimmune person, post-exposure prophylaxis may include:

• Hepatitis B immune globulin
• HBV vaccination

depending on vaccination status and the source patient.

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Hepatitis C Prevention

There is currently no vaccine for HCV.

Prevention relies on:

• Avoiding shared needles
• Sterile injection practices
• Safe blood screening
• Avoiding shared razors or blood-contaminated personal items
• Appropriate occupational precautions
• Safer sex in higher-risk situations

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Hepatitis D Prevention

There is no separate widely used HDV vaccine.

However:

HBV vaccination prevents HDV infection

because HDV cannot establish infection without HBV.

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Hepatitis E Prevention

Prevention relies mainly on:

• Safe drinking water
• Sanitation
• Proper food handling
• Avoidance of contaminated water

An HEV vaccine exists in limited geographic availability but is not routinely available worldwide.

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Etiology and Virology

HAV

HAV is:

• An RNA virus
• Non-enveloped
• A member of the Picornaviridae family

It does not cause chronic infection.

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HBV

HBV is:

• A partially double-stranded DNA virus
• A member of the Hepadnaviridae family
• Enveloped

Important viral markers include:

• HBsAg
• Anti-HBs
• Anti-HBc
• HBeAg
• Anti-HBe
• HBV DNA

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HCV

HCV is:

• An enveloped RNA virus
• A member of the Flaviviridae family

Multiple genotypes exist, although modern direct-acting antiviral therapy has reduced the practical importance of genotype in many treatment settings.

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HDV

HDV is:

• A small RNA virus
• Dependent on HBsAg from HBV for its envelope

Therefore it can occur only in a patient infected with HBV.

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HEV

HEV is:

• A non-enveloped RNA virus in blood
• Structurally quasi-enveloped during some phases of infection
• Classified within the Hepeviridae family

Most human disease is acute.

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Pathophysiology

The liver injury in viral hepatitis is largely mediated by the host immune response to infected hepatocytes, rather than direct viral destruction alone.

Typical pathologic changes include:

• Lobular inflammation
• Mononuclear-cell infiltration
• Hepatocyte degeneration
• Hepatocyte necrosis
• Kupffer-cell hyperplasia
• Cholestasis

In severe disease, extensive hepatic necrosis can result in:

• Coagulopathy
• Hypoglycemia
• Encephalopathy
• Multiorgan dysfunction
• Acute liver failure

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Clinical Presentation

The clinical manifestations of acute viral hepatitis are often similar regardless of the specific virus.

Many infections are asymptomatic or anicteric.

The illness may be divided into:

1. Prodromal phase
2. Icteric phase
3. Convalescent or posticteric phase

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Prodromal Phase

The prodrome usually precedes jaundice by approximately several days to 1–2 weeks.

Symptoms may include:

• Fatigue
• Malaise
• Anorexia
• Nausea
• Vomiting
• Fever
• Headache
• Myalgias
• Arthralgias
• Altered taste
• Altered smell
• Cough
• Coryza

Some patients report aversion to cigarettes or certain foods.

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Icteric Phase

As jaundice develops, some constitutional symptoms may improve.

Features may include:

• Jaundice
• Dark urine
• Pale stools
• Pruritus
• Right upper quadrant discomfort
• Hepatomegaly
• Tender liver

Not all patients become visibly jaundiced.

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Physical Examination

Possible findings include:

• Jaundice
• Hepatomegaly
• Right upper quadrant tenderness
• Splenomegaly
• Cervical lymphadenopathy

Splenomegaly and lymphadenopathy occur in a minority of patients.

In severe disease, look for:

• Confusion
• Asterixis
• Bleeding
• Hypotension
• Signs of cerebral edema
• Evidence of acute liver failure

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Incubation Periods

Approximate incubation periods are:

HAV

→ 15–50 days

HBV

→ Approximately 1–6 months

HCV

→ Approximately 2 weeks to 6 months

HDV

→ Depends on HBV coinfection or superinfection

HEV

→ Approximately 2–8 weeks

Incubation periods overlap and should not be used alone for diagnosis.

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Laboratory Findings in Acute Viral Hepatitis

Common findings include:

• Markedly elevated ALT
• Markedly elevated AST
• Hyperbilirubinemia
• Mild alkaline phosphatase elevation
• Relative lymphocytosis
• Atypical lymphocytes
• Mild leukopenia early in illness

Aminotransferases may rise before jaundice appears.

In hepatocellular injury:

ALT and AST are usually disproportionately elevated compared with alkaline phosphatase.

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Bilirubin

When jaundice develops, bilirubin may rise substantially.

Both conjugated and unconjugated fractions may increase, although conjugated hyperbilirubinemia is common in clinically significant hepatitis.

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Prothrombin Time and INR

A prolonged:

PT/INR

is an important marker of impaired hepatic synthetic function.

This is especially important in acute hepatitis because a rising INR may signal:

Acute liver failure

Aminotransferase levels alone do not reliably indicate severity.

A falling ALT in a deteriorating patient can actually be ominous if it reflects massive hepatocyte loss.

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Albumin

Albumin may remain relatively preserved in acute disease because of its long half-life.

Low albumin is more suggestive of:

• Chronic liver disease
• Prolonged severe illness
• Poor synthetic function

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Hypoglycemia

Hypoglycemia can occur in severe or fulminant hepatitis because of impaired hepatic glucose regulation.

It is an important marker of severe disease.

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Hepatitis A Diagnosis

The key test for acute HAV is:

IgM anti-HAV

This indicates recent or acute infection.

IgG anti-HAV

Indicates:

• Previous infection
• Vaccination
• Immunity

HAV does not cause chronic hepatitis.

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Hepatitis B Serology

HBV serology is particularly important and frequently tested.

HBsAg

Hepatitis B surface antigen

Indicates current HBV infection.

It appears early after infection.

Persistence for more than 6 months supports chronic infection.

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Anti-HBs

Antibody to hepatitis B surface antigen

Indicates immunity.

It can result from:

• Recovery from natural infection
• Vaccination

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Anti-HBc

Antibody to hepatitis B core antigen

This indicates exposure to actual HBV infection.

It is not produced by vaccination alone.

IgM anti-HBc

Suggests:

• Acute infection
• Recent infection
• Sometimes an acute flare of chronic HBV

Total or IgG anti-HBc

Usually persists for life after natural infection.

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HBV Window Period

An important examination concept is the window period.

During this period:

• HBsAg has disappeared
• Anti-HBs has not yet appeared

The key marker may therefore be:

IgM anti-HBc

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HBeAg

HBeAg generally indicates:

• Active viral replication
• Higher infectivity

However, some HBV variants replicate actively without detectable HBeAg, so modern assessment relies heavily on:

HBV DNA

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HBV DNA

HBV DNA measured by PCR reflects:

Viral replication

It is crucial for:

• Assessing disease activity
• Deciding treatment
• Monitoring response
• Evaluating transmission risk

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High-Yield HBV Serologic Patterns

Vaccinated

HBsAg: negative

Anti-HBc: negative

Anti-HBs: positive

→ Immune from vaccination

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Resolved natural infection

HBsAg: negative

Anti-HBc: positive

Anti-HBs: positive

→ Past infection, now immune

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Acute HBV

HBsAg: positive

IgM anti-HBc: positive

Anti-HBs: negative

→ Acute infection

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Chronic HBV

HBsAg: positive for >6 months

Anti-HBc: positive

Anti-HBs: negative

→ Chronic infection

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Hepatitis C Diagnosis

Initial screening is usually performed with:

Anti-HCV antibody

However, anti-HCV indicates exposure and does not distinguish:

• Active infection
• Resolved infection
• Successfully treated infection

Therefore a positive antibody test must be followed by:

HCV RNA

to determine whether active infection is present.

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HCV RNA

HCV RNA can become detectable very early after infection, before antibodies develop.

Therefore:

Recent exposure + negative antibody does not exclude acute HCV

HCV RNA should be checked if acute infection is suspected.

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HCV Genotype

Genotyping historically played a major role in treatment selection.

With modern pan-genotypic direct-acting antiviral regimens, genotype is less important than it once was, although it may still influence management in selected situations.

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Hepatitis D Diagnosis

Diagnosis may include:

• Anti-HDV antibodies
• HDV RNA

HDV RNA confirms active replication.

Because HDV requires HBV, patients should also undergo a complete HBV evaluation.

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Hepatitis E Diagnosis

Testing may include:

• IgM anti-HEV
• HEV RNA

IgM anti-HEV supports recent infection.

HEV RNA is especially useful in:

• Immunocompromised patients
• Suspected chronic infection

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Imaging

Ultrasound is not usually needed to diagnose uncomplicated viral hepatitis.

However, it may be useful to:

• Exclude biliary obstruction
• Evaluate liver morphology
• Assess portal or hepatic vessels
• Look for ascites
• Assess chronic liver disease

Doppler ultrasound may be added when vascular disease is a consideration.

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Liver Biopsy

Liver biopsy is rarely required in straightforward acute viral hepatitis.

It may be considered when:

• Diagnosis is uncertain
• Autoimmune hepatitis is suspected
• Chronic hepatitis requires staging
• Another liver disease needs exclusion

Noninvasive fibrosis assessment has replaced biopsy for many chronic hepatitis patients.

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Differential Diagnosis

The differential diagnosis of acute hepatitis includes:

• Drug-induced liver injury
• Acetaminophen toxicity
• Alcohol-associated hepatitis
• Autoimmune hepatitis
• Ischemic hepatitis
• Sepsis-associated liver injury
• Biliary obstruction
• Wilson disease
• EBV
• CMV
• HSV hepatitis
• Leptospirosis

Clinical context and targeted testing are essential.

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Treatment of Hepatitis A

There is no specific antiviral therapy for uncomplicated HAV.

Treatment is supportive and includes:

• Hydration
• Adequate nutrition
• Antiemetics if needed
• Avoidance of hepatotoxic substances
• Monitoring for acute liver failure

Most patients recover completely.

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Treatment of Acute Hepatitis B

Most immunocompetent adults with uncomplicated acute HBV recover spontaneously and do not require antiviral therapy.

Antiviral treatment is considered for:

• Severe acute hepatitis
• Protracted severe disease
• Acute liver failure

Potent nucleos(t)ide analogues such as:

• Tenofovir
• Entecavir

are generally preferred when antiviral treatment is indicated.

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Treatment of Chronic Hepatitis B

Modern first-line oral agents generally include potent drugs with a high barrier to resistance, particularly:

• Tenofovir disoproxil fumarate
• Tenofovir alafenamide
• Entecavir

Pegylated interferon may be used in selected patients.

Older drugs such as lamivudine are used much less frequently because resistance develops readily.

The major goals are:

• Suppression of HBV DNA
• Prevention of cirrhosis
• Prevention of liver failure
• Reduction of hepatocellular carcinoma risk
• HBeAg seroconversion when applicable
• Ideally, loss of HBsAg

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Treatment of Hepatitis C

The historical interferon-ribavirin regimens are now largely obsolete.

Modern HCV treatment uses:

Direct-acting antiviral agents (DAAs)

These regimens are:

• Oral
• Shorter
• Better tolerated
• Highly effective

Common modern pan-genotypic regimens include combinations such as:

• Sofosbuvir/velpatasvir
• Glecaprevir/pibrentasvir

Most appropriately treated patients can achieve cure rates exceeding 95%.

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Sustained Virologic Response

The goal of HCV therapy is:

Sustained virologic response (SVR)

This means HCV RNA remains undetectable after completion of therapy, typically assessed at least 12 weeks afterward.

SVR is considered a virologic cure.

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Treatment of Hepatitis D

Treatment of HDV has historically relied on pegylated interferon alfa in suitable patients.

Newer targeted therapies are becoming available in some regions, and specialist management is recommended.

The older statement that interferon gamma is standard therapy is not current practice.

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Treatment of Hepatitis E

Most immunocompetent patients require only:

• Supportive care

Chronic HEV may occur in immunocompromised patients, particularly transplant recipients.

Management may include:

• Reduction of immunosuppression when possible
• Ribavirin in selected chronic cases under specialist guidance

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Fulminant Hepatitis

Fulminant hepatitis refers to acute severe hepatic injury with:

• Coagulopathy
• Encephalopathy
• No established preexisting cirrhosis

Patients may develop:

• Cerebral edema
• Hypoglycemia
• Renal failure
• Metabolic disturbances
• Bleeding
• Multiorgan failure

These patients require urgent admission to a liver-transplant-capable center.

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Liver Transplantation

Liver transplantation may be life-saving in:

• Acute liver failure
• Decompensated cirrhosis
• Selected hepatocellular carcinoma
• End-stage chronic viral hepatitis

Early transplant referral is essential in fulminant disease.

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Hepatitis A Complications

Most HAV infections resolve completely.

Possible complications include:

• Prolonged cholestatic hepatitis
• Relapsing hepatitis
• Rare acute liver failure

HAV does not become chronic.

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Hepatitis B Complications

Chronic HBV may lead to:

• Chronic hepatitis
• Fibrosis
• Cirrhosis
• Portal hypertension
• Liver failure
• Hepatocellular carcinoma

HBV can cause hepatocellular carcinoma even in the absence of cirrhosis.

Extrahepatic manifestations include:

• Polyarteritis nodosa
• Glomerulonephritis
• Serum-sickness-like syndrome
• Arthralgias
• Cryoglobulinemia

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Hepatitis C Complications

Chronic HCV may lead to:

• Progressive fibrosis
• Cirrhosis
• Portal hypertension
• Liver failure
• Hepatocellular carcinoma

Important extrahepatic associations include:

• Mixed cryoglobulinemia
• Membranoproliferative glomerulonephritis
• Porphyria cutanea tarda
• Lichen planus
• B-cell lymphoma
• Insulin resistance and diabetes

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Hepatitis D Complications

HDV infection may accelerate HBV-associated liver disease.

Superinfection can produce:

• Severe acute hepatitis
• Rapid progression of fibrosis
• Cirrhosis
• Liver failure

HDV is generally more severe than HBV infection alone.

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Hepatitis E and Pregnancy

One of the classic high-yield features of HEV is severe disease during pregnancy.

In certain endemic settings, particularly with some HEV genotypes, pregnant women—especially in the second and third trimesters—have an increased risk of:

• Fulminant hepatitis
• Acute liver failure
• Maternal death
• Fetal complications

This association is particularly important in examinations.

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High-Yield Comparison

HAV

→ RNA

→ Fecal-oral

→ Acute only

→ No chronic infection

→ Vaccine available

HBV

→ DNA

→ Blood, sexual, perinatal

→ Acute or chronic

→ Vaccine available

→ Can cause cirrhosis and hepatocellular carcinoma

HCV

→ RNA

→ Mainly blood-borne

→ High rate of chronic infection

→ No vaccine

→ Curable with direct-acting antivirals

HDV

→ RNA

→ Requires HBV

→ Coinfection or superinfection

→ Prevented by HBV vaccination

HEV

→ RNA

→ Fecal-oral

→ Usually acute

→ Particularly severe in pregnancy

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High-Yield Clinical Approach

Acute hepatitis + recent contaminated food/water exposure

→ Think HAV or HEV

Acute hepatitis + sexual/blood exposure

→ Think HBV

Injection drug use + chronic hepatitis

→ Think HCV

HBsAg-positive patient with unexpectedly severe hepatitis

→ Consider HDV

Pregnant patient + acute hepatitis after travel to endemic region

→ Consider HEV

Positive anti-HCV

→ Confirm active disease with HCV RNA

HBsAg negative + anti-HBs positive + anti-HBc negative

→ Vaccinated

HBsAg negative + anti-HBs positive + anti-HBc positive

→ Resolved natural HBV infection

HBsAg positive + IgM anti-HBc positive

→ Acute HBV

HBsAg positive for >6 months

→ Chronic HBV

HBV window period

→ IgM anti-HBc may be the key positive marker

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Exam Essentials

HAV transmission:

→ Fecal-oral

HAV chronic infection:

→ Does not occur

HAV acute diagnostic marker:

→ IgM anti-HAV

HBV type:

→ DNA virus

HBV vaccination marker:

→ Anti-HBs only

Marker of natural HBV exposure:

→ Anti-HBc

HBV window-period marker:

→ IgM anti-HBc

HBV replication marker:

→ HBV DNA

HBeAg:

→ Usually indicates increased replication/infectivity

HCV screening test:

→ Anti-HCV antibody

HCV active infection test:

→ HCV RNA

HCV chronicity:

→ Common if untreated

Modern HCV treatment:

→ Direct-acting antivirals

HCV cure endpoint:

→ Sustained virologic response

HDV requirement:

→ HBV/HBsAg

Best prevention of HDV:

→ HBV vaccination

HEV transmission:

→ Fecal-oral

HEV major high-risk group for severe disease:

→ Pregnant women

Severe acute hepatitis marker:

→ Rising PT/INR

Fulminant hepatitis + encephalopathy:

→ Urgent liver-transplant-center referral