Phases of Hepatitis A Virus Related Hepatitis
Hepatitis A does not progress through distinct immunological phases like hepatitis B; instead, it follows a classical acute viral hepatitis course with four sequential clinical stages that typically resolve completely without chronic sequelae. 1, 2, 3
Clinical Stages of Hepatitis A
Stage 1: Incubation (Preclinical) Phase
- Duration: Average 28 days (range 15-50 days) after exposure 1
- Viral activity: Intensive virus replication occurs in the liver; HAV is excreted in bile and shed in stool 1, 2
- Peak infectivity: Occurs during the 2-week period before onset of jaundice or liver enzyme elevation, when stool viral concentration is highest 1
- Clinical presentation: Patient is asymptomatic but highly contagious 1
Stage 2: Prodromal (Preicteric) Phase
- Clinical manifestations: Abrupt onset of fever, malaise, anorexia, nausea, abdominal discomfort, and dark urine 1, 4
- Duration: Variable, typically several days before jaundice appears 4
- Viral shedding: Continues at high levels in stool; viremia persists at concentrations several orders of magnitude lower than in stool 1
- Serologic marker: IgM anti-HAV becomes detectable 5-10 days before symptom onset 1
Stage 3: Icteric Phase
- Jaundice development: Occurs in >70% of adults but only 30% of children aged <6 years 1
- Associated symptoms: Continued nausea, vomiting, abdominal discomfort, and light-colored stools 4
- Viral shedding: Concentration of virus in stool declines after jaundice appears, though children can shed HAV for up to 10 weeks after clinical illness onset 1
- Laboratory findings: Elevated liver enzymes (ALT/AST), hyperbilirubinemia 5
Stage 4: Recovery (Convalescent) Phase
- Typical duration: Signs and symptoms last <2 months in most patients 1
- Complete resolution: Occurs in the vast majority of cases without chronic sequelae or persistent infection 2, 3
- Lifelong immunity: IgG anti-HAV appears early and persists for life, providing permanent protection against reinfection 1, 2
Important Clinical Variants
Prolonged or Relapsing Disease
- Frequency: Occurs in 10-15% of symptomatic patients 1
- Duration: Can last up to 6 months 1
- Viral shedding: Recurrent shedding occurs during relapses 1
- Outcome: Still resolves completely without chronic infection 3
Cholestatic Hepatitis A
- Presentation: Prolonged jaundice with marked elevation of alkaline phosphatase and bilirubin 2
- Prognosis: Eventually resolves without permanent damage 2
Fulminant Hepatic Failure
- Overall incidence: Case-fatality ratio 0.3-0.6% 1
- High-risk groups: Adults aged >50 years (1.8% mortality rate) and persons with chronic liver disease 1, 3
- Clinical significance: Represents the most severe outcome requiring urgent evaluation for liver transplantation 3
Key Distinction from Hepatitis B
Unlike chronic hepatitis B, which progresses through five distinct immunological phases (immune tolerant, immune active HBeAg-positive, immune inactive, immune active HBeAg-negative, and HBsAg loss phases), hepatitis A never becomes chronic and does not exhibit phase-based progression. 1, 6, 7 Hepatitis A represents a self-limited acute infection that follows a predictable clinical course toward complete resolution 2, 3.