rotavirus, norwalk, astrovirus, type 40-41 adenovirus
Causes gastroenteritis. Diarrhea results in fluid loss and svr dehydration.
Mode of xmission of rotavirus
fecal-oral contamination via contaminated water.
Most common cause of severe diarrhea in children worldwide
typically infects intestines in children aged 6 mnths to 3 years. Season winter epid in temperate, yr round in tropical countries.
7 serogroups based on antigenic prop of VP6. A,B,C only human infxs. Most common globally is G1P8, G2P4, G3P8, G4P8
rotavirus infxns geography
Africa, Asia, latin america. Still common in developed countries. Major cause of hospitalization for gastroenteritis in US. India most afflicted.
Rotavirus molecular bio
Reoviridae, non enveloped, triple-layer virus, segemented ds RNA genome. Has own polymerase
Rotavirus clinical presentation
Watery stools & vomiting after 1-2 day incub period. Vomiting common and may b prolonged. Urine has high specific gravity and metabolic acidosis. No blood or fecal leukocytes.
ELISA for Ag in stool, EM (only for research lab), PCR: detec, ID all species, serotypes
FLuids and electorlytes
Rotavirus pathogenesis step 1
neutralizing Ab against VP4 +/- VP7 prevent viral binding/ penetration.
Rotavirus pathogenesis step 2
rotavirus replic inside enterocyte causes altered metab of enterocyte membrane proteins. Increases [ ] intracell Ca. Disrupts cytoskeleton and tight jxns, raising paracellular permeability.
Rotavirus pathogenesis step 3
intracellular viral replication inhibited by secretory anti-VP6 IgA.
Rotavirus pathogenesis step 4
cytokine secreting rotavirus spec T cells can inhibt viral rep.
Rotavirus pathogenesis step 5
if previous steps fail, replicat rotavirus produces non-structural protein 4 (NSP4), toxin which induces secretory non-CFTR mediated diarrhea. Can also stimulate enteric NS = secretory diarrhea and incr motility.
Rotavirus pathogenesis step 7
rotavirus kills host cell leading to further diarrhea.
Protection from rotavirus
natural infxn protects against severe disease associated w reinfeciton. Vp4 and Vp7 r targets for neutralizing Ab & either Ab response can mediate proteciton. Mucosal Ab not systemic provide proteciton.
early ones caused intussusception in small #. New ones Rotarix (crippled live strain), Rotateq (5 diff disabled rotavirus, combo human/cow).
norwalk or norwalk like, ssRNA + sense, naked, major cause of non-bacterial diarrhea in children >2 yo and adults.Most common cause of epidemics of viral gastroent in schools, camps, cruise ships etc.
based on clinical presentation and epidemiology & sx. Also absence of bacterial pathogens.
water diarrhea, nausea, vomiting, cramps, fever, headache, malaise
highly contagious: food, shellfish, fomites.
norovirus shape of virus
looks like cup like projxns on daffodils.
Four genogroups (1-4), 1,2,4 infect humans. Wide variety of differences between strains, so difficult to make a vaccine.
enterocytes of mid/ upper villus become infected leading to failure to absorb Na,water, peptides/ AA, sugars. Enteros die causing villus atrophy, crypt hyperplasia, some infilt of LP. ENS stimulated causing incrsd motility.
ssRNA + sense, naked, icosahedral capsid. 8 known serotypes. HAstV-1 most common. Most commonly affects child <2 yo, also eldely and immunodeficient.
similar to rotavirus but milder and usually self-limiting (shorter duration). Usually manifest in 2-3 days post-infxn.
astrovirus xmission and treatment
Xmission person to person and fecal:oral,, supportive only
watery diarrhea, mild vomiting, abd pain, headache, mild dehydration. Rarely requires hospitalization. Many infxns asymptomatic
fiberous projxns from each vertex, icosahedral capsid, dsDNA virus, non envelop, xmitted fecal-oral
adenovirus incubation and duration
1 week w/ 9-12 day duration.
diarrhea (less acute than rotavirus), can cause severe gut damage, vomiting, gastroenteritis.
adenovirus dx and tx
dx w/ EM, EIA for Ag in stool, fluid therapy to treat
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