Viral Gastroenteritis Flashcards
What is the most common transmission route for viral gastroenteritis?
fecal to oral route
True or false: viral gastroenteritis is only human to human transmission
false - some are animal to human
What type of diarrhea is caused by viral gastroenteritis?
secreotry
True or false: viral gastroenteritis diarrhea contains high levels of leukocytes?
false
True or false: viral gastroenteritis diarrhea typically does not contain blood.
true
What are the common symptoms of viral gastroenteritis?
nausea, vomiting, abdominal pain and diarrhea
What are the two most common viruses causing viral gastroenteritis?
rotavirus
norovirus
What are two lesser causes of viral gastroenteritis?
adenovirus
astrovirus
Which one has a predilection for the winter: rotavirus or norovirus?
rotavirus
norovirus happens all year round
Which one affects children?
rotavirus (younger than 5 typically_
What is norovirus particularly associated with?
contaminated food and water causes outbreaks in adults
What are the three big bacterial culprits for gastroenteritis?
salmonella
clostridium perfringens
camylobater
For rotavirus, RNA or DNA? genome?
RNA
DS segmented - class III
SUPER RARE
Describe the capsid for rotavirus.
it’s an icosahedral nucleocapsid with a DOUBLE SHELL!
The unique structure of rotavirus’s genome allows it to do what?
reassort - like with influenza
True or false: rotavirus affects humans and other vertebrates and often affects multiple species.
false - rotaviruses generally can affect both humans and other vertebrates but they exhibit substantial host-range restriction so the straings that affect humans only affect humans
What is the tropism for rotavirus?
mature absorptive villous epithelium of the upper two thirds of the small itnestine
What layer of the small intestine is rotavirus infection kept to?
the intestinal mucosa
Describe in general what happens in the cell after the rotavirus virion has entered it?
- capsid is shed and RNA genome released
- viral RNA-dependent RNA polymerase and other enzymes start to transcribe the RNA into mRNA
- mRNA is read by host machinery to translate into proteins
- virus particles generated
- leave the cell by lysis
True or false: the released virion particles are immediately infectious and will affect the cells in the same area?
false - the outer layer of the capsid needs to mature under lumen conditions before it can be infectious
will typically move down into the distal small bowel before that occurs
What characteristic does rotavirus have that is usually reserved for bacterial virulence factors?
it has a toxin
What is rotavirus’ toxin?
NSP4 - it will form a pore in the enterocyte so it lyses
How long does it take befor eyou can see cytoplasmic inclusions in the enterocytes where viral replication is taking place?
only 8 hours
At the height of infection with rotavirus, how many viral particles will be released per gram of stool?
10 billion
What are some of the reasons why rotavirus has such high death rates in the developing world?
- treatment is supportive so you need access to hospitals and clean water
- malnourishment makes it worse - especially vitamin deficiencies
What vitamin will often be given in addition to IV fluids for children with rotavirus in developing countries?
vitamin A
What are the two vaccines for rotavirus and how do they differ?
rotarix - human-infecting rotavirus proteins (attenuated)
rotateq - human and cow rotavirus proteins (even more attenuated)
Is norovirus an RNA or DNA virus? genome?
RNA virus SS+ nonsegmented - class IV (caliciviridae)
Describe the norovirus capsid.
it’s an icosahedral nucleocapsid
ragged outline (differs from other caliciviruses that have cup-shaped indentations or a star shape)
Is norovirus enveloped?
no
What symptoms will come with norovirus?
lower fever than rotavirus (not over 101)
severe vomiting
diarrhea, nausea, abdominal cramps
What piece of evidence gets at the massive prevalence of norovirus?
75% of people iwll have antibody response to norovirus by age 7
How long do symptoms last? How long do you shed the virus?
2-3 days
2-3 weeks
How many virus particles of norovirus are released per gram of stool?
100 billion
Why is immunity to norovirus so short lived?
the RNA-dependent RNA polymerase makes a lot of mustakes and introduces lots of mutations. DRIFT
this means there are TONS of different strains
What strain of norovirus emerged in march of 2012 and is not the dominant strain causing both cruise ship and land-based outbreaks worldwide?
GII.4 Syndey
What serotypes of adenovirus can cause gastroenteritis?
40, 41, 42
Is adenovirus a DNA or RNA virus? genome?
DNA
DS DNA linear (class I)
What is the capsid for adenovirus? Envelope?
icosahedral, nonenveloped
Do the enteric adenoviruses have a vaccine?
no
Although it’s not usually done, how can you make a laboratory diagnosis of adenovirus gastroenteritis?
you need to do direct analysis of the stool with immunoassays or PCR?DNA probes because the serotypes 40-42 don’t grow in culture
