Viral Diarrhea Flashcards
Susceptible vs permissive cells
Susceptible cells = has receptors and outer factors that allow for a cell to be infected
Permissive cells = has internal machinery (organelles, enzymes, etc.) that allow for the cell to be used for replication
both are required in order for a viral infection to actually occur
Case fatality rate (%)
Is an average percentage that takes a group of people/populations into account
- not applicable for individuals
high the number = more deadly
R0 definition
Basic virus reproductive number before intervention occurs
- essentially how many secondary infections does a virus cause from a single individual
higher the number = more infectious
Outbreak vs epidemics pandemic
Outbreak= a new virus/infection to a small area
Epidemic = a new virus in a larger area
Pandemic = a new virus on a global scale
Difference between RNA and DNA virus replication
RNA = done in the cytoplasm
DNA = done in the nucleus
also enveloped viruses are more susceptible to environmental factors, naked viruses are more resistant
Steps of viral replication
1) attachment
2) viral entry/invasion
3) uncoating
4) synthesis of virion proteins/NAs
5) virion assembly
6) release
Rotavirus
Reoviridae family virus
65nm
DsRNA virus that is segmented
-11 segments
Naked icosahedral
-3 capsid layers
there are 8 known strands (A-H) and RotaA is the #1 cause of diarrhea in children under 5 years old
RotaB is the form that affects adults, and is usually less severe
Rotavirus A proteins that are importaint
VP2 = inner capsid layer
VP1 = RNA dependent transcriptase
VP3 = RNA capping protein
VP4 = host cell recognition and inducing host cell endocytosis
Replication cycle of rotavirus
1) VP4 penetrates host cells after being cleaved by GI enzymes by host environment
2) loses outer capsid layers and VP1/4 start RNA transcription in-cytoplasm
- note: the rotavirus NEVER becomes fully uncoated
3) after enough has been made in the cytoplasm, becomes core proteins and goes into ER of host cells
4) gains envelope for short time*, then loses it and lysis cells to go out and infect more
Epidemiology and pathogensis of rotavirus
Most common in children from 6 months- 2 years (can go to 5 thou)
- this is because from birth -> 6 months = breast milk IgA
Is yearly but more common in winter areas
AVH antigens on erythrocytes and gastrocytes which is how rotavirus tries to find host cells
Pathogenesis:
- usually targets duodenum and jejunum villi (causes blunting of these villi)
- induces inflammation and decreases absorption of the small intestines
- lasts 2-12 days (assuming no immunocompromised)
- has NSP4 toxin = disrupts cytoskeleton and prevents absorption of water and electrolytes
Symptoms of rotavirus
Sudden onset vomiting Watery brown diarrhea -the diarrhea is very watery Tachycardia Fever Dehydration
diagnosed by ELISA (only if needed thou)
What is rotateq?
The rotavirus vaccine
- infects host cells still, but cant mount an infectious response/replicate well.
Contains VP7 bovine G6 and VP4 human P8
87% effective in VP4 strains only, 92% effective if contains VP4 and VP7
really promotes intestinal IgA/IgG production and maintenance
**Contraindications = SCID/immunocompromised patients
Norovirus
Calicivirdae family
Also known as SRSV/Norwalk-like virus
Is a naked (+) ssRNA virus
- icosahedral capsid
10 genogroups/49 genotypes
- G2, G4 and G1 are the only groups that are known to infect humans
is the most common viral cause of gastroenteritis worldwide (use to be Rotavirus, however vaccination fixed that)
Norovirus epidemiology and pathogenesis
Peaks in winter
- “winter-vomiting” disease
Very easily transmitted
- fecal-oral
- poor sanitization in foods
Targets brush border intestinal cells (primarily jejunum)
- ADH antigens are once again targeted
Symptoms of norovirus
Incubation = 12-72 hrs Recovery = 24-48 hrs
Symptoms:
- extreme vomiting/nausea (non-bloody)
- flu-like symptoms
- ab pain
- moderate-mild diarrhea (non-bloody)
Severe disease:
- fever
- everything above
- benign convulsions
Children are more likely to be asymptomatic than adults
most symptoms are severe, but is very short acting
