2.12 Enteric Viruses Flashcards
What is the underlying pathology in inflammatory versus non-inflammatory gastroenteritis?
Inflammatory: Damage to intestinal mucosa from pathogen invasion or cytotoxins.
Non-inflammatory: Malabsorption or enterotoxin-mediated fluid secretion without significant mucosal damage
What are the clinical signs of dehydration?
• Reduced urination or dark urine.
• Dry mouth and throat.
• Sunken eyes, absence of tears.
• Skin tenting.
• Rapid, weak pulse.
• Orthostatic hypotension
• Lethargy, irritability in children
Why is identifying dehydration important in viral gastroenteritis?
major complication due to fluid loss from diarrhea and vomiting; timely rehydration prevents severe outcomes
What are the main causative agents of viral gastroenteritis?
Rotavirus, norovirus, adenovirus (types 40, 41), and astrovirus
Astrovirus modes of transmission and pathogenesis
Fecal-oral; damages intestinal epithelial cells
Rotavirus modes of transmission and pathogenesis
Fecal-oral; infects small intestine, causing villi destruction and malabsorptive diarrhea
Norovirus modes of transmission and pathogenesis
Fecal-oral, airborne droplets; binds histo-blood group antigens, disrupting intestinal cells
Adenovirus modes of transmission and pathogenesis
Fecal-oral; replicates in gut, causing watery diarrhea.
What is the peak age of incidence and seasonal variation for rotavirus?
Infants and young children; peaks in winter and spring (Dec–Jun)
peak age of incidence and seasonal variation for norovirus?
All ages; outbreaks occur Nov–Apr
What is the peak age of incidence and seasonal variation for adenovirus?
Primarily young children; no seasonal variation
What are the route of administration, age recommendations, and production of the rotavirus vaccine?
Oral
RotaTeq (3 doses: 2, 4, 6 months), Rotarix (2 doses: 2, 4 months). Must start before 15 weeks of age.
Live attenuated, human and bovine strains
common diagnostic methods for viral gastroenteritis?
Rotavirus: Enzyme immunoassay (EIA), RT-PCR.
Norovirus: Real-time qPCR, conventional RT-PCR outbreaks.
Adenovirus: PCR, EIA, antigen detection.
Astrovirus: EIA, immune electron microscopy
Hepatitis type that is Fecal-oral; severe in pregnancy?
HEV
What two kinds of hepatitis are blood borne with one with chronic infection risk and another with chronic liver damage?
HBV (infection)
HCV (liver damage)
Which type of hepatitis is fecal oral and self limiting?
HAV
Which kind of hepatitis requires co-infection with HBV?
HDV
What are the hallmark symptoms of acute hepatitis?
Jaundice (skin/eye yellowing).
Dark urine, pale stools.
RUQ pain.
Fatigue, nausea, vomiting.
Fever during prodromal phase
What are the key differences between HAV and HEV infections?
HAV: Common in developed and developing nations, resolves spontaneously, vaccine available.
HEV: Widespread in developing countries, severe in pregnancy, limited vaccine availability (China only) .
How are HAV transmitted and prevented?
Fecal-oral. HAV via close contact
Prevent with Vaccination, hygiene.
How are HEV transmitted and prevented?
Fecal-oral. via contaminated water/food.
Hygiene, avoid unsafe water/meat .
significance of elevated bilirubin (>3mg/dL)?
Indicates jaundice; reflects impaired hepatic excretion
significance of elevated liver enzymes (AST/ALT>1000U/L)?
Hepatocyte injury. ALT often higher in viral hepatitis
What is a common characteristic of viruses that cause gastroenteritis?
Nonenveloped
They survive longer in the environment and as contagious fomites
Who are most susceptible to viral gastroenteritis?
Infants and young children
What is the most defining clinical feature of viral gastroenteritis?
Vomiting
+ds RNA Virus and Segmented
Rotavirus
What is notable about a segmented virus?
Can change their genotype easily
+ss RNA ?
Norovirus, Astrovirus
HAV and HEV
DsDNA non enveloped?
Adenoviruses
Most viruses that cause gastroenteritis have what transmission pattern?
Water borne and food borne
Leading cause of severe diarrhea in children in developing world versus USA?
Rotavirus (develop) vs. Norovirus (USA)
Key rotavirus structural proteins for vaccine development as neutralizing antibody targets?
VP4 (P pro) and VP7 (G pro)
What contributed to rapid spread of rotavirus?
Very high infectivity (low infectious dose) and high number shed in stool
What do rotaviruses target and how do they cause damage?
Villus epithelial cells with NSP4 enetrotoxin (& ca+ release)
Most common test for rotavirus infection?
EIA stool sample
What is unique about Noroviruses that allows them to survive in harsh environments?
Heat and acid stable
What is essential for the norovirus to bind and infect?
ABH and Lewis blood group antigens (@saliva and mucosa)
“Winter vomiting disease”?
Norovirus
Common settings for norovirus outbreaks?
Long term care facilities, restaurants and catering… cruise ships 6%
Preferred diagnostic test for norovirus?
Realtime qPCR Assay
Adenovirus serotypes common in viral gastroenteroritis especially in young children?
40 and 41
What is special about adenovirus attachment and toxicity?
Fiber proteins
Best diagnostic test for adenovirus?
Stool but PCR done too
What virus appears like a “star” under electron microscopy?
Astroviruses
What virus looked like a “wheel” with electron microscopy?
Rotavirus
What are key features of norovirus clinically?
Affects all ages and projectile vomiting
What gastroenteritis viruses are year round?
Adenovirus, Astrovirus, and Sapovirus
What is bilirubin normally conjugated to by hepatocytes in order to be excreted?
Glucuronic acid
What is a sign of liver damage in if found in urinalysis ?
Unconjugated bilirubin
What family does HAV belong to?
Picovirinidae
Where does HAV replicate?
Hepatocytes and Kupffer cells
What causes the liver damage in HAV?
Immune response (NK and CD8 T cells)
How long are you protected for after recovering from HAV?
For life (Anti-HAV IgG antibodies)
Is there a vaccine for HAV?
Yup, universal infant recommendation and high risk adults
When does the HAV post exposure prophylaxis need to be administered?
Within 2 weeks
What are the main HEV genotypes?
1&2 = human infection (develop)
3&4 = zoonotic (industrial)
Most cases of HEV in the US are?
Travel related
What are main clinal feature of HEV?
Jaundice and pruritus**
What is the diagnostic tools for HAV and HEV?
HAV/HEV-IgM
RT-PCR
Unvaccinated child under <5 years with watery diarrhea and viral origin should hint at?
Rotavirus
