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Category: Food Microbiology
Foodborne Viral Pathogens, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555819972/9781555819965.ch23-1.gif /docserver/preview/fulltext/10.1128/9781555819972/9781555819965.ch23-2.gifAbstract:
Human enteric viruses are responsible for substantial morbidity worldwide. Transmitted predominantly by the fecal-oral route and exclusively in association with human feces and/or vomitus, these viruses come into contact with humans by a variety of routes, including the consumption of contaminated foods. From an epidemiologic perspective, the most significant of these are human noroviruses, which are the most common cause of acute gastroenteritis worldwide and are now recognized as the leading causes of foodborne illness. Enteric viruses can be transmitted directly by person-to-person contact or indirectly by consumption of contaminated food or water or contact with fomites. The usual source of enteric virus contamination is human fecal matter, which can easily harbor up to 1010 genomic RNA copies per gram when shed by infected individuals. Human enteric viruses have properties that are distinct from those of bacterial foodborne pathogens. Viruses are usually species specific and tissue tropic, meaning that the human enteric viruses are believed to infect only humans. Since they must resist the enzymatic conditions and pH extremes encountered in the gastrointestinal tract, enteric viruses are also resistant to a wide range of commonly used food-processing, preservation, and storage treatments.
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Norwalk virus genome organization (adapted from reference 10 ). VPg, genome-linked virion protein. ORF1 encodes a polyprotein that is posttranslationally cleaved into the nonstructural proteins helicase (with a predicted nucleotide triphosphate-binding domain [NTPase]), proteinase (Pro), and RNA-dependent RNA polymerase (Pol). ORF2 encodes capsid protein, which is translated into major and minor structural proteins consisting of shell and protruding domains. N, NH2-terminal arm. ORF3 encodes a basic protein of unknown function.
HAV genome organization (adapted from reference 121 ; see also reference 114 ). The 5′UTR is 624 to 1,199 nt long. VPg, genome-linked virion protein, 22 to 24 amino acids. The single ORF encodes a polyprotein that posttranslationally cleaved into VP1, VP2, and VP3, which form the capsid; VP4 is the inner surface capsid protein. 2A, unknown function; 2B, RNA synthesis and cell membrane permeability; 2C, RNA replication; 3A and 3B, RNA replication proteins, cofactor for 3D; 3C, viral proteinases; 3D, RNA-dependent RNA polymerase. The poly(A) tail is about 35 to 100 nt long; the 3′UTR is 47 to 125 nt long.
Transmission routes of foodborne viruses.
Flow diagram of the ISO method for the detection of HAV and NoV in food and bottled-water samples. Image adapted from ISO/TS 15216-1:2017, annex A ( 251 ). TGBE, Tris-glycine-beef extract; PEG, polyethylene glycol.