Pathogen. The hepatitis A virus differs in some characteristics from entero-viruses, to which group it was long considered to belong. Growth in cell cultures requires long adaptation. Only one serotype is known to date.
Pathogenesis and clinical picture. The clinical picture of hepatitis A, so-called epidemic or infectious hepatitis, differs in no major particulars from that of hepatitis B (p. 429). The disease nearly always takes a benign course. Only a small number of fulminant (and sometimes lethal) or chronic courses have been described. The pathogenic process at first corresponds to that of the enteroviruses, whereby hepatitis A replicates in the intestine and then, after a brief viremic episode, attacks its target organ, the liver. Disease manifestation with this pathogen, unlike most of the enteroviruses but similar to hepatitis B, involves immunological processes.
Diagnosis is based on IgM detection due to the early presence of these antibodies in patient serum, in fact so early that a lack of hepatitis A antibodies at the onset of clinical manifestations excludes hepatitis A.
Epidemiology and prevention. Transmission is by food and water or in the form of smear infections. Infection with hepatitis A shows a clear north-south gradient: it has become virtually a travelers' disease in central Europe. Imported cases frequently cause minor outbreaks in families or schools. Active immunization with an inactivated HAV vaccine is available.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.