Viral gastroenteritis Flashcards
are all viruses obligate intracellular parasites
yes
- reproduce in living cells only
- no independent metabolism
do viruses replicate via binary fision?
no, progeny are created in an assembly line fashion
central goal of virtually all viruses
rapidly replicate new virions at the expense of the host cell
Lytic interactions
are those that cause the death and lysis of the host cell
Stages of Lytic Viral Replication
- Attachment Specific receptors arrayed at cell surface - determines host and tissue specificity (trophism) and mode of spread in host
- Penetration/entry
- Uncoating
- Synthesis of virion components
- Maturation/Release
when virus is added to a host, there is one step sudden upsurge that different than other organisms. describe it
- latent period: relative virus count is 0
- assembly and release: viral count increases sharply
what are non lytic host interactions
- viruses may produce long-term associations with host cells that are not lethal to the host.
- The virus remains associated with the host cell, but the virus genes are largely unexpressed
- association is stable and long-term, but may be terminated under environmental conditions.
Persistent infections
- Infection without cell death; unusual virus-host interaction in which the virus is found in a long-term association with the host.
what are the three subclasses of persistent infections
- latent infection
- chronic infection
- transforming infection
what are Latent Infections; give an example
- intermittent acute episodes of virus production between which there is an almost complete absence of virus particles and very limited viral macromolecular synthesis
- Herpes simplex, Varicella-zoster
what are chronic infections. Give an example
- nonlytic production of virus, continued presence of high numbers of virus particles during periods in which clinical disease is absent
- Hepatitis B virus
what are transforming infections. Give an example
- infected cells are immortalized and properties altered (transformed) to those of cancer cells.
- human papilloma virus
gastroenteritis
- inflammation of stomach and intestine
- one of the most common diseases of humans
- frequent cause of mortality in children in developing nations
gastroenteritis symptoms
- acute watery diarrhea is main feature of viral disease
- nausea, vomiting, cramps, malaise, anorexia, myalgia, headache
in gastroenteritis, viral replication occurs where
Viral replication occurs in small intestine epithelial cells
gastroenteritis
- length of incubation period
- length of disease
- 15-48 hrs incubation period
- Disease duration is typically short (3-5 days)
- Virus may be shed at low levels for days to weeks after illness
tests for diagnose viral infections
Virus protein antigen detection
- enzyme immunoassay (rotazyme)
- latex agglutination screen test
- Assays are best described as generally insensitive
treatment of gastroenteritis
- Primary therapy is oral re-hydration
- Solutions of electrolytes plus sugar
- ***There is no role for antibiotics in uncomplicated viral disease
etiology of infant diarrhea (gastroenteritis)
Rotavirus and enteric adenoviruses
- The most frequent cause of infantile gastroenteritis is rotavirus, the most frequent US strain is G1
- First two years of life
- Disease transmission even in locations in which clean water and food are available
etiology of gastroenteritis caused by outbreaks (fecally-contaminated food)
the Noroviruses - Norwalk, SRSV
- seen commonly in raw shellfish
prevention strategies for rotavirus
- vaccines are now available for dominant rotavirus strains G1-G4, G9
- Rotateq
- 3 doses beginning at 6-12 weeks with a 4-10 week interval between doses
- Rotarix
- 2 doses
- Rotateq
Rotavirus: pathophysiology and course of illness
- Infection of small intestine villi enterocytes, disrupt osmotic function
- 5-7 day course of fever, vomiting, diarrhea
which bacteria causes “winter vomiting disease”
Rotavirus causes predictable, annual epidemics during each winter season leading to the name ‘winter vomiting disease.’
structure of enteric adenovirus
Double stranded DNA virus
length of sickness caused by enteric adenovirus
- endemic diarrhea in infants
- Extended period: 5-12 days of diarrhea, fever, and vomiting
length of illness caused by the caliciviruses (now referred to as Norovirus)
24-48 hours
- typically mild and self-limited
caliciviruses (now referred to as Norovirus) primarily infects what age group
older children and adults
caliciviruses (now referred to as Norovirus) is associated with what
associated with food (shellfish)
distinguishing feature of caliciviruses (now referred to as Norovirus)
extraordinarily resistant to inactivation
name the caliciviruses
Norwalk and SRSV’s (SRSV = small round shaped viruses) - now grouped under Norovirus
