16.
The appearance of symptoms and infectivity ranges from 15 to 45 days following
the first exposure to the hepatitis A virus. The virus is rapidly cleared from the
body at the onset of symptoms. The highest period of infectivity occurs during the
late incubation period. The patient is considered potentially infectious for up to 2
weeks after the onset of symptoms. There are no reported cases of a chronic
carrier (infection longer than 6 months) HAV state.
(para 7-16)
17.
Considering HAV immunological assays, the anti-HAV IgM detects IgM antibody
produced in the initial response to hepatitis A antigen. It is specific for diagnosing
or confirming an acute HAV infection. The anti-HAV measures total antibody (IgM
and IgG) to hepatitis A antigen. It is an indicator of recent infection as well as past
infection. It is primarily useful in confirming previous exposure and immunity to
hepatitis A.
(para 7-17)
18.
The hepatitis B virus consists of a central core containing the core antigen
(HBcAg) and a surrounding envelope containing the surface antigen (HBsAg).
DNA, hepatitis Be antigen, and an DNA polymerase are located in the central
core. The intact virus particle containing these components is referred to as the
"Dane particle."
(para 7-18)
19.
Hepatitis B virus is predominantly transmitted via the parenteral route. Parenteral
transmission occurs mainly through exposure to contaminated blood or blood
products (blood transfusions, dialysis patients, hemophiliacs, infected needles,
etc.). Though transmission appears to be primarily parenteral, HBV can also be
transmitted through a number of nonparenteral routes such as close intimate
contact.
(para 7-19)
The length of the incubation period for HBV correlates inversely with the amount of
20.
virus to which the individual is exposed. (Large dose of HBV = short incubation
time.) The average incubation period for hepatitis B is about 45 days with a typical
range from 30 to 120. Hepatitis B is potentially highly infectious. As long as
HBsAg is detectable, the individual should be considered infectious. A chronic
carrier state does exist for hepatitis B infections.
(para 7-20)
MD0838
7-24