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Chapter 17 : Hepatitis A and E Viruses
Category: Applied and Industrial Microbiology; Food Microbiology
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In the early 1940s, "infectious" and "serum" hepatitis was identified based on mode of transmission. Enteric hepatitis includes two types: hepatitis A virus (HAV) and hepatitis E virus (HEV), both of which can be foodborne and waterborne. The genetic characteristics of the enteric hepatitis viruses are discussed in this chapter. Enteric hepatitis infections may also develop asymptomatically; chronic disease has so far never been reported. The absence of a lipid envelope helps ensure the stability of the enteric hepatitis agents in the presence of biliary salts, which is not the case for serum hepatitis viruses. Alum and chlorine treatment prevented bacterial infections in 1955 and 1956, but 30,000 cases of hepatitis occurred among the population. Irrigation of vegetables as well as washing and processing of any food that is consumed raw with HAV- or HEV-contaminated water could lead to enteric hepatitis outbreaks. Enteric hepatitis viruses may become water contaminants through the discharge of untreated sewage and treated wastewater. Molecular epidemiology points to a geographical distribution of hepatitis A and E viruses. Globalization, climate change, and the inherent genetic variability of these viruses may promote the emergence of new variants. All this calls for the need to trace and characterize circulating enteric hepatitis viruses.
Organization of the hepatitis A virus genome. Top: Diagram of the virus genome depicting the genome-linked VPg protein at the 5′ end and the poly A tail at the 3′ end. Bottom: Proteolytic processing pattern of the polyprotein resulting after translation.
Organization of the hepatitis E virus genome. The viral genome, with its capped 5′ end and its polyadenylated 3′ end, encodes 3 ORFs. Nonstructural proteins are encoded by ORF-1 and are translated from the genomic RNA. Capsid proteins are encoded by ORF-2 and are expressed from a 2.0-kb subgenomic RNA, which also expresses an immunogenic protein of unknown function encoded by ORF-3. The role of a 3.7-subgenomic RNA also found in infected cells is yet to be determined.
Examples of documented hepatitis A water and foodborne transmission
Examples of documented hepatitis E water and foodborne transmission