Calicviruses Notes

NOTES NOTES CALICVIRUSES MICROBE OVERVIEW Genetic material ▪ Single-stranded RNA viruses Morphology ▪ Small, icosahedral, non-enveloped Taxonomy ▪ Genera: Norovirus, Sapovirus, Lagovirus, Nebovirus, Vesivirus Transmission ▪ Ingestion → small intestine → villi infection → malabsorption → osmotic diarrhea NOROVIRUS osms.it/norovirus PATHOLOGY & CAUSES ▪ Virus known as viral gastroenteritis agent ▫ AKA Norwalk virus ▪ Classified into seven genogroups ▫ I, II, IV → cause human disease Transmission ▪ Fecal-oral ▫ Infected individual: virus in stool < four weeks ▫ Immunocompetent individual: peak concentration 2–5 days post-infection ▪ Direct person-to-person ▪ Contaminated food, water, fomite ▫ Contaminated water in leafy vegetables, oysters, raspberries ▫ Prepared food → contaminated at point of service (e.g. salads, sandwiches) ▪ Droplet spread from vomitus Pathogenesis ▪ Ingestion → small intestine villi infection → disruption of epithelium, anion transport system → malabsorption of D-xylose, fat → osmotic diarrhea 330 OSMOSIS.ORG Small intestine histopathology ▪ Villous shortening, epithelial vacuolization, crypt hypertrophy, microvilli brush border loss, intercellular space widening, lymphocytic proliferation of lamina propria RISK FACTORS ▪ Blood group antigens ▫ Viral binding preference for A, B antigens genogroup-determinant ▪ Close-quarter residence (e.g. nursing homes, cruise ships) COMPLICATIONS ▪ Severe dehydration, malnutrition, persistent disease (immunosuppressed individuals) SIGNS & SYMPTOMS ▪ 12–48 hour incubation period ▪ Acute onset vomiting ▫ Nonbloody, nonbilious ▪ Watery diarrhea ▫ Nonbloody ▪ Fever, abdominal pain, myalgia, malaise

Chapter 59 Calicviruses DIAGNOSIS ▪ History ▫ Pathogen contact, contaminated food source LAB RESULTS ▪ Reverse transcriptase polymerase chain reaction (RT-PCR) ▫ Stool OTHER INTERVENTIONS ▪ Fluid maintenance, repletion ▫ From oral intake → IV fluids ▪ Electrolyte balance Prevention ▪ Hand hygiene ▪ Environmental fecal contact decontamination ▪ Limited pathogen contact TREATMENT ▪ No cure MEDICATIONS ▪ Antimotility agents ▪ Antiemetics ▫ Reserved for individuals unable to take oral hydration OSMOSIS.ORG 331