Term
| what are the 4 major groups of viruses causing diarrhea? |
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Definition
| rotaviruses, caliciviruses, astroviruses, enteric adenoviruses |
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Term
| what population is affected by rotavirus infections? |
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Definition
| children. accounts for 40-60% of acute gastroenteritis cases in children <2 years of age. responsible for most severe diarrhea in children and infants |
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Term
| what demographic is affected by caliciviruses? |
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Definition
| older children and adults (all ages!!) |
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Term
| what demographic is affected by astroviruses? |
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Definition
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Term
| what demographic is affected by enteric adenoviruses? |
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Definition
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Term
| how are rotaviruses spread? |
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Definition
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Term
| how are caliciviruses spread? |
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Definition
| sporadically (outbreaks); direct fecal oral; indirect through contaminated water and food (shellfish) food can be contaminated at the source or during preparation by food handlers, contact with fomites |
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Term
| how are astroviruses spread |
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Definition
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Term
| how are enteric adenoviruses spread |
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Definition
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Term
| what do rotaviruses look like under the microscope? |
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Definition
| (reoviridae family) spherical, icosahedral, non-enveloped, DOUBLE SHELLED, wheel-like distinct appearance under EM |
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Term
| describe the genome of the rotavirus |
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Definition
| 11 segments of dsRNA; high potential to produce new strains (d/t shuffling/reassortment of genes of 2 diff serotypes) structural proteins (VP4, VP7 for outer and inner capsids); core proteins (VP2, VP6, VP1, VP3); nonstructural proteins (NSP1-5) |
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Term
| which is the only virus that we have a vaccine against? |
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Definition
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Term
| rotavirus is naked (non-enveloped), what characteristics does this bestow on the virus? |
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Definition
| resistant to alcohol, organic solvents that would dissolve or destroy other viruses (resistant to disinfectants) |
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Term
| what part of the rotavirus antigenically defines the different strains of the virus? |
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Definition
| components of the protein coat/capsid |
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Term
| what is the one major rotavirus strain that accounts for about 50% of infections now? |
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Definition
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Term
| briefly describe rotavirus replication |
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Definition
| receptors on intestinal epithelial cells recognize VP8 protein on rotavirus via its sialic acid and ganglioside compnents --> virus enters via endocytosis or direct penetration of the cell membrane --> virus uncoats --> uncoated shell particles can start transcribing +mRNA from the -mRNA (so many strands to copy, mistakes made, reassortment of genome occurs here in this early phase of transcription that leads to creation of new strains) --> secondary stage of transcription producing additional mRNA for viral components (transcription takes place in viroplasm) --> viruses bud through ER, acquiring lipid membrane that does not persist in mature particles --> additional steps, final peptides added --> epithelial cell may just fall apart or some particles come out before host cell destroyed |
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Term
| describe the pathogenesis of rotavirus |
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Definition
| infects upper 2/3 of duodenum --> as more infectious particles released, undergo further replication in distal areas --> destruction of epithelial cells, blunting of villi, variable infiltration with monos, pmns (gastric acid and colonic mucosa remain unaffected) --> decreased absorptive surface, decreased prod of brush border enzymes --> transient malabsorptive state (fats/sugars) --> severe diarrhea, vomiting, abd pain |
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Term
| what is the host defense against rotavirus? |
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Definition
| adults create long lasting abs, with type-specific sIgA produced in GALT (peyers patches). infant protection is breastmilk of mother (transfers sIgA if mother has been exposed) |
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Term
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Definition
| antigen enzyme immunoassay of stool specimen. tx is supportive (REHYDRATION!), detecting organism doesnt do much in terms of indicating what treatment to use etc bc its supportive. but knowing that its rotavirus causes you to take rehydration more seriously than say an adenovirus infection, but can prob tell its rotavirus from clinical picture. |
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Term
| what are the 3 rotavirus vaccines? |
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Definition
| RRV-TV (rotashield) - oral live tetravalent rhesus-human vaccine withdrawn after association with intussusception; PRV (rotateq) oral live pentavalent bovine-human vaccine; HRV (rotatrix) oral live human attenuated monovalent vaccine |
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Term
| describe some characteristics of the caliciviruses |
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Definition
| small, naked, icosahedral, very resistant to heat, acid, organic solvents |
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Term
| what are the 2 genera of caliciviruses? |
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Definition
| noroviruses (affect all age groups) and sapoviruses (affect more frequently children <5 yo) |
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Term
| what is the genetic material of caliciviruses (norovirus) |
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Definition
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Term
| describe the genome of calicivirus/norovirus |
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Definition
| high genetic diversity, 5 phylogenic clusters (genogroups G1-GV), at least 27 genotypes. human disease assoc with genogroups G1, GII, GIV. genotype II.4 predominates in developed world |
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Term
| sx of calicivirus/norovirus? |
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Definition
| vomiting, diarrhea, nausea, abdominal cramps, systemic sx (fever, chills, etc). sudden onset of vomiting more common in kids, sudden onset of diarrhea more common in adults. no blood, no mucus, no leukocytes. asymptomatic in 1/3 of patients. fever in 50%, self limited. |
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Term
| what are the host defenses against calicivirus/norovirus? |
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Definition
| not understood. resistance develops against the same, but not heterologous strains lasts from 4-5 months to 2-3 years |
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Term
| diagnosis, tx, prevention of calicivirus/norovirus |
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Definition
| electron microscopy, PCR, enzyme immunoassays (no vaccine, no tx) |
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Term
| describe the morphology of astroviruses |
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Definition
| non-enveloped (means resistant to acid, alkaline pH, ether, heat, organic solvents), 5 or 6 pointed star shaped virus particles |
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Term
| describe the genetic material of astroviruses |
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Definition
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Term
| which virus is widely distributed in nature, mammals birds? |
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Definition
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Term
| describe the morphology of the adenovirus |
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Definition
| large, non-enveloped, icosahedral, well-defined paracrystalline structure of protein coat w/hexons and pentons (penton fiber=most antigenic) |
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Term
| describe the genetic material of the adenovirus |
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Definition
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Term
| what is the main tropism for adenovirus? (and minor) |
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Definition
| major: respiratory system (resp inf); minor: conjunctivitis, mild gastroenteritis (has much broader host range with regard to tissue tropism - more variable than other viruses) |
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Term
| which virus can be oncogenic? |
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Definition
| adenovrius -no oncogenic in humans, but can transform cells in culture |
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Term
| which are the adenovirus serotypes that cause enteric infections? |
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Definition
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Term
| which virus has potential for gene/cancer therapy? |
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Definition
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Term
| sx of adenovirus infection |
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Definition
| respiratory, conjunctivitis, very mild gasteroenteritis, only serious threat in immunocompromised |
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