Hepatitis A: CDC Viral Hepatitis Serology Training

Hepatitis A: CDC Viral Hepatitis Serology Training


(electronic music) Hepatitis A, a liver disease caused by infection with the hepatitis A virus, referred to as HAV, is diagnosed by the use of
appropriate serologic tests. The diagnosis of acute hepatitis A is confirmed during the acute
or early convalescent phase of HAV infection by the
presence of IgM antibodies to HAV, referred to as IgM anti-HAV. This serologic marker is
shown by the pink hatched line and is usually present
from five to ten days before the onset of clinical symptoms, noted by the purple bar. The median onset of symptoms
is 28 days after infection, noted by the vertical dotted line, but can range from 15 to 50 days. IgM anti-HAV usually declines
to undetectable levels within six months after infection. IgG antibodies to HAV, referred to as IgG anti-HAV, shown in the black hatched line, begin to rise at or right before the onset of clinical illness, and persist to provide lifelong immunity. IgG anti-HAV is also produced
following immunization with hepatitis A vaccine. Some commercial tests only
measure total anti-HAV, which includes both IgM and IgG anti-HAV. Serologic tests for IgG anti-HAV or total anti-HAV may be used to determine whether a patient has been
infected with HAV in the past, or remains susceptible to infection, but are not helpful in
diagnosing acute illness. In persons with acute hepatitis A, HAV replicates in the liver, is excreted in the bile, and is found in highest
concentrations in stool, and thus peak infectivity, during the two-week period prior to onset of clinical illness. This period of viral shedding in stool is shown by the orange bar. Virus concentration in
stool declines rapidly after jaundice appears in adults, although shedding may be prolonged in infected infants and children, even up to several months after the onset of clinical illness. Chronic shedding of HAV
in stool does not occur. However, shedding can occur in persons who have relapsing illness. ALT, shown in blue, stands for alanine aminotransferase, a liver enzyme that is elevated when the liver is inflamed. Viremia, shown by the green bar, occurs soon after infection and persists through the peak period of liver enzyme elevation. However, methods to detect viremia are generally limited
to research laboratories and are not commonly used
for diagnosing illness. This segment is now complete. (electronic music)

One thought on “Hepatitis A: CDC Viral Hepatitis Serology Training

  1. Simply excellent. Very grateful for clear, concise and well presented video. Thank you for the great channel. 😊😊 4/9/2019

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