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13 Cards in this Set

  • Front
  • Back
Rotaviruses Properties and Replication
- 11 pieces of dsRNA -> high rate of reassortment in dual infection(w/in groups not b/w)
- groups share cross reactive Ags (A, B, C in humans, A in US)
- lots of serotypes in each group
- 3 layer icosahedral w/ spikes (must be cleaved to infect)
- cytocidal, replicate in the intestinal epi cell cytoplasm
- use viral encoded enzymes
Rotaviruses Pathogenesis
- ingested (fecal-oral) -> viruses replicate in the columnar epi of intestines
- villi lose surface epi cells -> malabsorption -> diarrhea
- glycoprotein 4 may be enterotoxin -> diarrhea
- die from dehydration
- no residual damage(cells rapidly ->normal after clearing)
Rotaviruses Clinical Signs
- subclinical to fatal diarrhea
- infants(<6mo) asymptomatic, maternal antibody
- severe almost exclusively seen in the 6-24 months
- later infections are mild (unless immunocomp/old, but not big in HIV)
- asymptomatic incubation -> vomit for 3days
- fever/diarrhea begins later(lasts up to 1wk)
- give supportive fluid therapy to resolve
Rotaviruses Diagnosis
- detection of rotavirus (EM of stools), or viral antigen (ELISA or PCR)
Rotaviruses Epidemiology
- major cause of severe diarrhea everywhere
- mainly kids <2yrs
-cooler months=more freq(in developed)
- first appears in the SW then sweeps NE
- infection from as few as 10 virus particles
- 48 hour asympt incubation, w/ high level of shedding(lasts throughout clinical phase & days after symptoms end
- subsequent infection = subclinical from childhood immunity(exposed to lots, yrs later may re-infect, mildly)
- Aerosol and formite spread
- resistant to inactivation
- can retain infectivity for seven months at Room T
- frequent nosocomial infection
Rotaviruses Treatment and Prevention
- fluid/electrolytes replacement
- vaccine should prevent severe diarrhea in first 2 years (most critical)
- there was a failed vaccine that was withdrawn(ettenuated rhesus monky rotavirus(ARMR))
Norwalk Agent Properties and Replication
- calicivirus, naked, (+) sense ssRNA
- fastidious in their growth requirements, replicate poorly in cell culture
- humans only reservoir
Norwalk Agent Pathogenesis
- villi of the SI broaden and become blunted
- epithelial mucosa remains intact(opp of rotav.), but malabsorption -> diarrhea
- nausea and vomiting due to affected gastric motor function
Norwalk Agent Clinical Manifestations and immunity
- 24 hour incubation
- lasts 24-48 hours once symptoms begin
- nausea, vomiting(kids), diarrhea(adults)
- no immunity if previous exposure, maybe due to different serotype or genetic # of virus receptors
Norwalk Agent Diagnosis
- often the diagnosis in GI outbreak if:
1) others have been ruled out
2) more than 50% are vomiting
3) its an epidemic fashion, follows point-source exposure by 24-48 hrs
Norwalk Agent Epidemiology
- not major cause of infantile diarrhea
- outbreaks in schools, institutions, camps, families
- gets adults and school age children
- epidemics from contaminated shellfish(raw=most freq cause of gastroenteritis outbreaks), food, or water
- 1/3 to 2/3 of GI epidemics
Norwalk Agent Treatment and Prevention
- oral fluid replacement
- Pepto-Bismol (bismuth salicylate) to reduce symptoms
- just be sanitary to prevent
- do acute respiratory syndromes and epidemic keratoconjunctivitis
- 2 serotypes (of dozens) associated with gastroenteritis
- really only do nosocomial diarrhea in young children