Unit 1: Viral GI Infections Flashcards
All viruses are obligate _______________
Obligate Intracellular Parasites
Reproduction and metabolic activities inside living cells only
Outside of the host, a virus only persists waiting for another host
Viruses have NO host-independent metabolic activities - host provides ribosomes, energy, all precursor molecules
The term “virus” is derived from …
Latin word for poison
What do we mean when we refer to viruses as “filterable agents”?
The ability of viruses to passage through fine pore filters that would retain bacteria
Viruses replicate in a pattern …
That is fundamentally different from all other living (cellular) organisms.
Progeny are created in an assembly line fashion and are not generated by binary fission of the parent.
__________ interactions are those that cause the death and lysis of the host cell.
Lytic interactions
The central goal of virtually all viruses is to quickly replicate virus at the expense of the host cell.
This activity may result in the lysis and death of the cell.
Alternative viral replication strategies that do not always kill the host are known.
The same general pattern of lytic viral replication holds for all viruses:
1) Attachment - specific receptors arrayed at cell surface determine host and tissue specificity (trophies must) and mode of spread in host
2) Penetration/entry
3) Uncoating
4) Synthesis of vision components
5) Maturation/Release
What are non-lytic infections
In addition to acute lytic infections, viruses may produce long-term associations with host cells that are not lethal to the host.
Virus remains associated with eh host cell, but the virus genes are largely unexpressed. The association is stable and long-term, but may be terminated under some conditions.
What are persistent infections?
Infection without cell death.
Unusual virus-host interaction in which the virus is found in a long-term association with the host.
Three subclasses of persistent infections
1) Latent Infections - intermittent acute episodes of virus production between which there is an almost complete absence of virus particles and very limited viral macro molecular synthesis (ex - Herpes simplex, varicella zoster)
2) Chronic infections - no lytic production of virus, continued presence of high numbers of virus particles during periods in which clinical disease is absent (ex - Hep B)
3) Transforming - infected cells are immortalized and properties altered (transformed) to those of cancer cells.
Frequent cause of mortality in children in developing nations
Gastroenteritis
One of the most common diseases of humans
Symptoms range from mild diarrhea to severe disease requiring hospitalization
Clinical manifestations of viral gastroenteritis
Sx: nausea, diarrhea, vomiting, cramps, malaise, anorexia, myalgia, h/a
ACUTE, PROFUSE, AND WATERY DIARRHEA is the main feature of viral disease.
Clinical presentation so of disease caused by different viral agents is indistinguishable. So how do we tell them apart?
EPIDEMIOLOGY varies and offered clues for diagnosis.
Consider travel history, occupation, age, etc.
In the US, the major of gastroenteritis disease cases are probably…..
Viral. Duh.
In gastroenteritis cases, viral replication occurs in…
The small intestine epithelial cells
15-48 hour incubation period
Disease duration is typically short (3-5 days)
Virus may be shed at low levels for DAYSTO WEEKS after illness
Patient groups at high risk for viral enteritis
Hospital wards Daycare centers Nursing homes Immunosuppression individuals Travelers Military
