Hepatitis A virus can be detected in the blood and feces during the incubation phase. Viremia and fecal shedding of HAV usually peak before the onset of symptoms and are usually present at only low levels by the time jaundice appears. Serum anti-HAV IgM is typically measurable 5 to 10 days prior to the onset of symptoms. Serum IgM peaks by 3 months and, in most cases, is undetectable by 6 months. Serum levels of anti-HAV IgG begin to rise later in the incubation period and remain elevated, conferring lifelong immunity. Serum ALT levels increase prior to the beginning of symptoms and peak 3 to 10 days after symptom onset.
Abbreviations: HAV = hepatitis A virus; ALT= alanine aminotransferase