Pathogenesis of Viral Diseases

Questions and Answers

What is the primary impact of viral infections on the host?

They often result in subclinical infections. (correct)

They cause immediate death of the host.

They only affect the respiratory system.

They always lead to severe clinical illness.

Which step in viral pathogenesis immediately follows entry and primary replication?

Viral spread and cell tropism (correct)

Cell injury and clinical illness

Recovery from infection

Viral shedding

What must viruses overcome to infect the respiratory tract?

Lack of blood supply

High temperatures

Non-specific inhibitory mechanisms (correct)

An acidic environment

What characteristic is common for viruses that infect via the gastrointestinal tract?

They must withstand hostile conditions. Signup and view all the answers

Which of the following routes is most commonly associated with blood-borne viral infections?

Injection through needles or transfusions Signup and view all the answers

What is the significance of a virus needing to cause minimal harm to the host?

It allows the host to support further viral spread. Signup and view all the answers

What forms of entry do most viruses require to infect through the skin?

A cut or breach in the skin Signup and view all the answers

What describes the term 'cell tropism' in the context of viral infections?

The preference of a virus for specific cell types Signup and view all the answers

Which of the following diseases is associated with the measles virus infection?

Subacute sclerosing panencephalitis Signup and view all the answers

How do some viruses manage to persist and cause chronic infections?

By constantly mutating to escape detection Signup and view all the answers

What mechanism is employed by CMV to downregulate the host immune system?

Coding for proteins that reduce MHC class I expression Signup and view all the answers

What common feature do prions share with conventional viruses?

Both can cause central nervous system diseases Signup and view all the answers

Which of the following is true about progressive multifocal leukoencephalopathy (PML)?

It is caused by JC virus, a papovavirus Signup and view all the answers

Which of the following statements about acute infections is incorrect?

Acute infections are associated with prolonged duration Signup and view all the answers

What is the most common direct damage caused by viruses to host cells?

Death of the host cell through apoptosis Signup and view all the answers

Which of the following mechanisms does NOT typically contribute to indirect cell damage from viral infection?

Excessive protein synthesis in infected cells Signup and view all the answers

What role does cellular immunity play in viral infections?

It is crucial in clearing the virus from the body. Signup and view all the answers

Which factor is primarily responsible for the recovery from an acute viral infection?

Host immune response mechanisms Signup and view all the answers

How might a virus provoke an autoimmune response in the host?

By mimicking host proteins and exposing protected sites Signup and view all the answers

What is the effect of the immune response during persistent viral infections?

It may cause more pathology in some infections. Signup and view all the answers

Which process is NOT a direct cause of cell death in viral infections?

Activation of cytotoxic T lymphocytes Signup and view all the answers

Which immune component is critical for protecting against reinfection after a viral infection?

Humeral immunity Signup and view all the answers

Which of the following viruses spread via the respiratory route, causing systemic infections but also having a transient primary viraemia?

Measles virus Signup and view all the answers

What factors contribute to the spread of viruses within the body?

All of the above Signup and view all the answers

Which of the following is NOT a factor determining viral tropism?

Specific viral genome sequences Signup and view all the answers

Which of these statements regarding viral spread is TRUE?

Measles, varicella-zoster, and rubella viruses have a transient primary viraemia, allowing them to replicate in the RES. Signup and view all the answers

Which of the following is a factor contributing to the development of disease after viral infection?

All of the above Signup and view all the answers

How does the genitourinary tract compare to other body regions in terms of its susceptibility to viral infections?

It is less frequently exposed to extraneous viruses than other body regions. Signup and view all the answers

What is the primary reason viruses can spread further from the initial infection site?

Viruses can utilize virus-encoded proteins to facilitate their transport within the cell and enhance their spread via blood or nerves. Signup and view all the answers

What is the role of the Reticuloendothelial System (RES) in viral infections?

The RES serves as a temporary site of viral replication for certain viruses during their incubation period. Signup and view all the answers

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?

By increasing the number of cells infected by facilitating the binding of virus-antibody complexes to cell surface Fc receptors. Signup and view all the answers

Which of the following viral infections is NOT directly associated with the immune complex deposition mechanism of immune pathological response?

Rabies Signup and view all the answers

In the context of viral persistence, what distinguishes chronic infection from chronic carrier state?

Chronic infection typically results in severe clinical features, while chronic carrier state is usually asymptomatic. Signup and view all the answers

Which of the following best describes the pathogenesis of a slow virus infection?

The virus remains dormant for a prolonged period before causing disease. Signup and view all the answers

Which of the following viral infections is an example of a latent infection?

Herpes Simplex Virus type 1 (HSV-1) Signup and view all the answers

What is the primary mechanism by which exaggerated T-cytotoxic cell responses contribute to enhanced viral injury?

By directly destroying infected cells, leading to tissue damage and inflammation. Signup and view all the answers

In the context of viral shedding, what makes rabies infection unique?

Rabies is a dead-end infection in humans, meaning there is no viral shedding from infected individuals. Signup and view all the answers

Which of the following statements is TRUE regarding viral persistence and the immune system?

The immune system can adapt to the presence of certain viruses, allowing for chronic carrier state. Signup and view all the answers

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

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
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
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
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
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.