What are the phases of hepatitis A virus associated hepatitis?

Phases of Hepatitis A Virus Associated Hepatitis

Overview

Hepatitis A infection progresses through four distinct sequential clinical phases: incubation phase, prodromal phase, icteric phase, and recovery phase, with the entire illness typically resolving within 2 months in most patients. 1

The Four Clinical Phases

1. Incubation Phase

• Duration: Average of 28 days (range: 15-50 days) 2, 3
• Characteristics: Asymptomatic period after viral exposure 1
• Viral activity: HAV replicates in the liver and begins shedding in stool 2
• Peak infectivity: Occurs during the final 2 weeks of this phase, before any symptoms appear or liver enzymes elevate 2
• Clinical significance: Patients are most contagious during this asymptomatic period, making transmission control challenging 3

2. Prodromal Phase

• Duration: 1-7 days before jaundice onset 2
• Clinical features: Abrupt onset of nonspecific symptoms including:
  • Fever 2, 3
  • Malaise and fatigue 2
  • Anorexia 2, 3
  • Nausea and vomiting 2
  • Abdominal discomfort 2, 3
  • Dark urine (bilirubinuria) - often the first symptom prompting medical attention 2
• Viral shedding: Continues at high concentrations in stool 2
• Viremia: Present and persists through this phase, though at much lower concentrations than in stool 2

3. Icteric Phase

• Onset: Within a few days after dark urine appears 2
• Clinical manifestations:
  • Jaundice of sclera, skin, and mucous membranes 2
  • Clay-colored (acholic) stools 2
  • Hepatomegaly on physical examination 2
  • Pruritus (uncommon) 2
• Age-related presentation:
  • Children <6 years: 70% have asymptomatic infections; when symptomatic, typically no jaundice 2, 3
  • Older children and adults: >70% develop jaundice 2, 3, 1
• Laboratory findings: Elevated liver enzymes (ALT, AST) and bilirubin 1
• Duration: Stool discoloration resolves within 2-3 weeks, indicating disease resolution 2

4. Recovery Phase

• Duration: Most patients significantly improve within 3-4 weeks 2
• Characteristics:
  • Resolution of jaundice 1
  • Normalization of liver enzymes 2
  • Complete symptom resolution 1
  • Development of lifelong immunity (IgG anti-HAV) 2, 3
• Typical course: Signs and symptoms last <2 months in 85-90% of patients 2, 1

Atypical Clinical Courses

Prolonged or Relapsing Disease

• Frequency: Occurs in 10-15% of symptomatic patients 2, 1
• Duration: Can last up to 6 months 2, 1
• Pattern:
  • Single relapse in most cases 4, 5
  • Multiple relapses (polyphasic disease) in approximately 20% of relapsing cases 2
• Relapse timing: Usually occurs within 3 weeks after initial remission 4
• Clinical features during relapse:
  • Generally milder than initial phase 4
  • More pronounced cholestatic features 4
  • Viral shedding continues in stool 2, 4
  • IgM anti-HAV remains detectable 4, 5
• Prognosis: Almost always benign with complete recovery 2, 4

Cholestatic Hepatitis

• Characteristics: Prolonged jaundice with marked elevation of bilirubin 2
• Management consideration: Short course of rapidly tapered corticosteroids can reduce symptoms and hasten resolution 2, 6

Fulminant Hepatitis A

• Frequency: 0.3-0.6% overall; 1.8% in adults >50 years 2, 1
• Clinical features:
  • Increasing severity of jaundice 2
  • Deterioration in liver function 2
  • Coagulation abnormalities 2
  • Hepatic encephalopathy 2
• High-risk groups:
  • Adults >50 years 2, 1
  • Patients with chronic liver disease (hepatitis B, hepatitis C) 2, 1
• Outcome: Spontaneous recovery in 30-60% of cases with full liver function restoration 2

Diagnostic Considerations

Serologic Testing

• IgM anti-HAV: Required for definitive diagnosis of acute infection 2, 3, 1
  • Becomes detectable 5-10 days before symptom onset 2, 3
  • Persists for several months, including during relapses 4, 5
• IgG anti-HAV: Appears early in infection, remains detectable lifelong, provides permanent immunity 2, 3, 1

Key Clinical Pitfalls

• Asymptomatic transmission: Peak infectivity occurs before symptoms appear, making early identification difficult 2
• Prolonged viral shedding in children: Can shed virus up to 10 weeks after illness onset 2, 3
• Relapse recognition: Biochemical relapse may occur without symptoms; requires monitoring of liver enzymes for several months 4, 5
• Age-dependent presentation: Young children are often asymptomatic carriers who can transmit infection to adults 2, 3