Clinical Information

HAV is a small, non-enveloped RNA virus belonging to the picornavirus family. HAV causes a self-limited illness and is almost always transmitted via the fecal-oral route. HAV infection is often mild with an acute onset but cannot be distinguished clinically from other types of acute viral hepatitis. Symptoms include fever, malaise, nausea, and abdominal pain. The presenting symptoms are often followed days later by dark urine, pale stools, and jaundice. Recent or acute infection with HAV is differentiated from other types of viral hepatitis through detection of IgM antibody to HAV (IgM anti-HAV) or HAV ribonucleic acid (RNA).

Early in the illness, IgM anti-HAV is the predominant antibody. It becomes detectable within 5 to 10 days of the onset of symptoms and can persist for several (approximately three) months. IgM anti-HAV normally becomes undetectable within 6 months after infection. IgG anti-HAV becomes detectable shortly after IgM appears. As IgM anti-HAV declines to undetectable levels, IgG anti-HAV becomes the predominant antibody. The presence of IgG anti-HAV with a nonreactive IgM anti-HAV test result implies past infection with HAV or vaccination against HAV, both scenarios indicating immunity against the virus. In acute infection, IgG anti-HAV detection is used in conjunction with IgM anti-HAV and other viral hepatitis markers (e.g., aspartate transaminase, alanine transaminase, bilirubin, etc.) for differential diagnosis.