Hepatitis A Contagiousness Timeline
Hepatitis A is most contagious during the 2-week period BEFORE jaundice onset or liver enzyme elevation, with viral shedding declining substantially after jaundice appears, though children can continue shedding virus for up to 10 weeks after symptom onset. 1
Peak Infectivity Period
The highest concentration of virus in stool occurs 14 to 21 days before jaundice onset through approximately 8 days after jaundice appears. 1 This means infected individuals are maximally contagious during the prodromal phase when symptoms are vague and nonspecific (fever, malaise, nausea), making transmission control particularly challenging. 1
Post-Jaundice Viral Shedding
After jaundice develops, viral concentration in stool declines significantly, but shedding continues:
- Adults: Viral shedding decreases rapidly after jaundice onset 1
- Children: Can shed HAV for up to 10 weeks after clinical illness begins 1, 2
- Neonates: In rare nosocomial outbreaks, infants infected as neonates have shed virus for up to 6 months 1
Critical Clinical Implications
The 2-week pre-jaundice window represents the period of greatest transmission risk, which is why hepatitis A outbreaks in daycare settings are often detected only when adult contacts become symptomatic—the pediatric index cases have already passed their peak infectious period. 1, 3
Age-Related Detection Challenges
- Children <6 years: Over 90% have asymptomatic infections, making them efficient silent transmitters 1, 2
- Adults: >70% develop jaundice, making clinical recognition more likely 1, 2
Relapsing Disease Considerations
Approximately 10-15% of patients experience relapsing disease lasting up to 6 months, and recurrent viral shedding occurs during these relapses. 1, 2 This means infection control precautions may need to extend beyond the initial illness in these cases.
Post-Exposure Prophylaxis Window
Immune globulin or hepatitis A vaccine must be administered within 2 weeks of exposure to be effective, which aligns with the pre-symptomatic infectious period. 3, 4 Once a contact develops symptoms, they have likely already been exposed during the source patient's peak infectious phase.
Common Pitfall
The major clinical pitfall is assuming patients become contagious when they develop jaundice—by the time jaundice appears, peak infectivity has already passed. 1, 5 This explains why isolation precautions focused solely on jaundiced patients are inadequate for outbreak control, and why prophylaxis of exposed contacts must occur rapidly after case identification.