Viruses of Diarrhea Flashcards
4 Grops of Viruses that are important causes of GI diseases:
- Rotaviruses
- Calicivirus
- Astroviruses
- Adenoviruses
Rotavirus
- Rotavirus genus of the Reoviridae family
- ( + ) ds RNA icosohedral naked segmented
Rotavirus Structure
- lsmall, spherical, 65-75 nm in diameter, (wheel-shaped)
- 11 segments of double stranded RNA
- double capsid (inner and outer shells),
- outer capsid, VP4 and VP7, target for neutralizing antibodies
Rotavirus Replication
- replicates in the cytoplasm
- virus release by host cell lysis
Rotavirus Clinical Disease
- Rotavirus infections are common during cooler months among infants and young children 1 to 24 months of age
- The virus primarily localizes in the duodenum and proximal jejunum causing destruction of villous epithelial cells
Rotavirus Incubation
•1-3 days
Rotavirus Symptoms
- Abrupt onset, vomiting followed by diarrhea (copious, watery, brown stools), life-threatening in malnourished or an immunodeficient, normal duration of diarrhea 5-8 days
- In severe cases, the stools may be clear; referred as hakuri, the “white stool diarrhea.”
- Viral excretion usually lasts 2 to 12 days
Rotavirus Immune Response
- Rotavirus infection responds with type-specific humoral antibodies that probably does not last for a lifetime after the first infection.
- Recovery from the first infection provides 38% protection against infection, 77% protection against diarrhea, and 87% protection against severe diarrhea.
- Subsequent infections give long-term immunity.
- Type-specific IgA antibodies are produced in the intestinal tract, correlate best with immunity.
- Breastfeeding also seems to play a protective role against rotavirus disease in young infants.
Rotavirus Diagnosis
- Detect virus in stool
- RIA, ELISA, EM, PCR
Rotavirus Treatment
- No specific treatment
- Use of fluids and electrolytes is needed in severe cases and can be life saving.
Rotavirus Prevention
- Highly infectious and can spread quickly in family and institutional settings.
- Control consists of rigorous hygienic measures: hand washing and disposal of enteric excretions.
- Live oral vaccine given in 3 doses, first at 6-12 weeks and 2nd and 3rd doses at 4-10 weeks interval
Norwalk like Viruses
- Norwalk like Viruses - Norovirus and Sapovirus genera of the Caliciviridae family
- ( + ) ss RNA icosohedral naked
Norovirus Structure
•Round, small ss (+) RNA particles, naked capsid (27-38nm), 2 capsid proteins; Vp1 and VP2, replicate in the cytoplasm like positive sense RNA virus, assembly in the cytoplasm and release upon cell lysis
Norovirus (Calicivirus) Epidemiology
•Norovirus the leading cause of viral gastroenteritis in children following rotavirus vaccine
Norovirus (Calicivirus) Symptoms
•1-2 day incubation, abrupt onset, vomiting and diarrhea, normal duration 1-2 days, seen in older children and adults, no enterotoxic features
