Hepatitis A Incubation Period
The incubation period for hepatitis A is 15 to 50 days, with an average of 28 days. 1
Key Clinical Timeline
The incubation period represents the time from viral exposure to symptom onset, and understanding this timeline is critical for:
Contact tracing and prophylaxis decisions: The 15-50 day range (average 28 days) means exposed individuals remain at risk for up to 7 weeks after contact. 2
Peak infectivity timing: Patients are most contagious during the 2-week period before jaundice or liver enzyme elevation occurs, which falls within the late incubation period. 2 This means infected individuals are spreading virus before they know they're sick—a critical public health consideration.
Age-Dependent Clinical Presentation
The incubation period remains consistent across age groups, but symptom manifestation differs dramatically:
Children under 6 years: Over 90% remain asymptomatic throughout infection, making them silent spreaders. 2
Older children and adults: More than 70% develop jaundice and symptomatic disease. 2
Initial prodrome: After the incubation period, a 1-7 day prodromal illness with anorexia, malaise, fever, and nausea typically precedes jaundice. 2
Practical Implications for Prophylaxis
The 28-day average incubation period directly informs post-exposure prophylaxis guidelines:
Immune globulin (IG) must be administered within 2 weeks of exposure to be effective, as this targets the early-to-mid incubation period before viral replication becomes overwhelming. 3
Hepatitis A vaccine provides protection within 4 weeks of the first dose, which aligns with the average incubation period, making it suitable for pre-exposure prophylaxis in travelers. 3
Viral Shedding Duration
While the incubation period ends when symptoms begin, viral shedding patterns extend beyond: