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Chapter 3 : Enterically Transmitted Hepatitis
Category: Applied and Industrial Microbiology; Food Microbiology
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The genomic sequences of various hepatitis A virus (HAV) genotypes are, however, quite highly conserved in the 5' untranslated region, making it the most suitable genomic region for designing assays for detection and quantification of the virus in various clinical and other specimens. HAV infection induces the development of specific immunoglobulin M (IgM) and IgG antibodies. Immunization with HAV vaccines is associated with the development of IgG antibodies against the viral structural proteins. Humans are the only source of HAV. After excretion in human feces, the virus can contaminate food items though several possible routes. The detection of HAV in food material and environmental specimens is therefore based on specific methods such as reverse transcription-PCR (RT-PCR) for detecting small quantities of viral nucleic acids; these methods involve amplification of viral genomic sequences, making them highly sensitive. Adequate heating and proper handling of foods may be expected to reduce the risk of food-borne transmission of hepatitis E virus (HEV) infection, although direct evidence supporting the efficacy of these measures is lacking. Attempts at identifying novel viruses responsible for parenterally transmitted hepatitis led to the identification of genetic material of several putative viruses, such as hepatitis G virus/GB virus and TT virus. HAV and HEV are common causes of enterically transmitted viral hepatitis. Both these viruses have RNA genomes, are excreted in feces of the infected persons, and are transmitted by the fecal-oral route.
Epidemiological patterns of HAV infection.
Characteristics of major hepatitis viruses