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Questions and Answers
What is the primary impact of viral infections on the host?
What is the primary impact of viral infections on the host?
Which step in viral pathogenesis immediately follows entry and primary replication?
Which step in viral pathogenesis immediately follows entry and primary replication?
What must viruses overcome to infect the respiratory tract?
What must viruses overcome to infect the respiratory tract?
What characteristic is common for viruses that infect via the gastrointestinal tract?
What characteristic is common for viruses that infect via the gastrointestinal tract?
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Which of the following routes is most commonly associated with blood-borne viral infections?
Which of the following routes is most commonly associated with blood-borne viral infections?
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What is the significance of a virus needing to cause minimal harm to the host?
What is the significance of a virus needing to cause minimal harm to the host?
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What forms of entry do most viruses require to infect through the skin?
What forms of entry do most viruses require to infect through the skin?
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What describes the term 'cell tropism' in the context of viral infections?
What describes the term 'cell tropism' in the context of viral infections?
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Which of the following diseases is associated with the measles virus infection?
Which of the following diseases is associated with the measles virus infection?
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How do some viruses manage to persist and cause chronic infections?
How do some viruses manage to persist and cause chronic infections?
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What mechanism is employed by CMV to downregulate the host immune system?
What mechanism is employed by CMV to downregulate the host immune system?
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What common feature do prions share with conventional viruses?
What common feature do prions share with conventional viruses?
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Which of the following is true about progressive multifocal leukoencephalopathy (PML)?
Which of the following is true about progressive multifocal leukoencephalopathy (PML)?
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Which of the following statements about acute infections is incorrect?
Which of the following statements about acute infections is incorrect?
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What is the most common direct damage caused by viruses to host cells?
What is the most common direct damage caused by viruses to host cells?
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Which of the following mechanisms does NOT typically contribute to indirect cell damage from viral infection?
Which of the following mechanisms does NOT typically contribute to indirect cell damage from viral infection?
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What role does cellular immunity play in viral infections?
What role does cellular immunity play in viral infections?
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Which factor is primarily responsible for the recovery from an acute viral infection?
Which factor is primarily responsible for the recovery from an acute viral infection?
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How might a virus provoke an autoimmune response in the host?
How might a virus provoke an autoimmune response in the host?
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What is the effect of the immune response during persistent viral infections?
What is the effect of the immune response during persistent viral infections?
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Which process is NOT a direct cause of cell death in viral infections?
Which process is NOT a direct cause of cell death in viral infections?
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Which immune component is critical for protecting against reinfection after a viral infection?
Which immune component is critical for protecting against reinfection after a viral infection?
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Which of the following viruses spread via the respiratory route, causing systemic infections but also having a transient primary viraemia?
Which of the following viruses spread via the respiratory route, causing systemic infections but also having a transient primary viraemia?
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What factors contribute to the spread of viruses within the body?
What factors contribute to the spread of viruses within the body?
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Which of the following is NOT a factor determining viral tropism?
Which of the following is NOT a factor determining viral tropism?
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Which of these statements regarding viral spread is TRUE?
Which of these statements regarding viral spread is TRUE?
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Which of the following is a factor contributing to the development of disease after viral infection?
Which of the following is a factor contributing to the development of disease after viral infection?
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How does the genitourinary tract compare to other body regions in terms of its susceptibility to viral infections?
How does the genitourinary tract compare to other body regions in terms of its susceptibility to viral infections?
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What is the primary reason viruses can spread further from the initial infection site?
What is the primary reason viruses can spread further from the initial infection site?
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What is the role of the Reticuloendothelial System (RES) in viral infections?
What is the role of the Reticuloendothelial System (RES) in viral infections?
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In the context of immune pathological response, how can excessive antibody-dependent cellular cytotoxicity (ADCC) or complement-mediated cell lysis lead to enhanced viral injury?
In the context of immune pathological response, how can excessive antibody-dependent cellular cytotoxicity (ADCC) or complement-mediated cell lysis lead to enhanced viral injury?
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Which of the following viral infections is NOT directly associated with the immune complex deposition mechanism of immune pathological response?
Which of the following viral infections is NOT directly associated with the immune complex deposition mechanism of immune pathological response?
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In the context of viral persistence, what distinguishes chronic infection from chronic carrier state?
In the context of viral persistence, what distinguishes chronic infection from chronic carrier state?
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Which of the following best describes the pathogenesis of a slow virus infection?
Which of the following best describes the pathogenesis of a slow virus infection?
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Which of the following viral infections is an example of a latent infection?
Which of the following viral infections is an example of a latent infection?
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What is the primary mechanism by which exaggerated T-cytotoxic cell responses contribute to enhanced viral injury?
What is the primary mechanism by which exaggerated T-cytotoxic cell responses contribute to enhanced viral injury?
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In the context of viral shedding, what makes rabies infection unique?
In the context of viral shedding, what makes rabies infection unique?
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Which of the following statements is TRUE regarding viral persistence and the immune system?
Which of the following statements is TRUE regarding viral persistence and the immune system?
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Study Notes
Viral Pathogenesis
- Viral pathogenesis is the process by which a viral infection leads to disease
- Most viral infections are subclinical, meaning they don't cause significant harm to the host
- The consequences of viral infections depend on the interplay between viral and host factors
Steps in Viral Pathogenesis
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Entry and primary replication:
- Most viruses enter the host through mucosa of respiratory or gastrointestinal tract
- Viruses replicate at primary sites, producing disease at the portal of entry with no further systemic spread
- Some viruses are introduced into the bloodstream by needles, blood transfusion, or insect vectors
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Viral spread and cell tropism:
- Many viruses cause localized infections, unable to spread
- Some viruses use virus-encoded proteins to direct their transport within the cell, enhancing spread
- Other viruses, like CMV, EBV, and HIV, are carried by infected blood cells to distant parts
- Measles virus, varicella-zoster virus, and rubella virus spread via respiratory route, causing systemic infections
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Cell injury and clinical illness:
- Destruction of virus-infected cells in target tissue and physiologic alterations produced in the host are responsible for disease
- Cells respond to viral infections in three ways: no apparent change, death, or transformation
- Direct cell damage can result from diversion of cell energy, rupture of infected cell, shutoff of cell macromolecular synthesis, or competition of viral mRNA for cellular ribosomes
- Indirect cell damage can result from integration of viral genome, induction of mutations in host genome, inflammation, or host immune response
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Recovery from infection:
- Host either submits or recovers from viral infection
- Recovery mechanisms involve humeral, cell-mediated immunity, interferon, and other cytokines
- Immune response has the greatest impact on the outcome of infection
- In acute infection, recovery is associated with viral clearance
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Viral shedding:
- Last stage in pathogenesis is shedding of virus into the environment
- Shedding usually occurs from body surfaces involved in viral entry
- Person becomes infectious to contacts during this stage
Viral Persistence
- Chronic infection: virus continuously detected, often at low levels, with severe or mild clinical features
- Chronic carrier: patient continues to produce significant amounts of virus for a long period
- Latent infections: virus persists in occult or cryptic form, with intermittent flare-ups
- Slow virus infections: prolonged period between initial infection and onset of disease, measured in years
Mechanisms of Viral Persistence
- Immune evasion: viruses escape immune system by constantly mutating
- Immune suppression: viruses downregulate host immune system
- Genomic integration: viruses integrate into host genome and replicate with cells
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Description
This quiz covers the process of viral pathogenesis, including the steps involved and the factors that influence it. Learn about how viral infections lead to disease and the interplay between viral and host factors.