Viral Pathogenesis
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The ability of a virus to cause disease in a host is referred to:

  • Pathogen
  • Pathogenicity (correct)
  • Pathogenesis
  • Virulence

    • The virus which causes disease is called

  • Pathogenicity
  • Virulence
  • Pathogen (correct)
  • Pathogenesis

    • The manner/mechanism of development of a disease is called:

  • Pathogenesis (correct)
  • Pathogen
  • Pathogenecity
  • Virulence

    • The term ________ is used as a quantatitive or relative measure of the degree of pathogenecity of the infecting virus

    <p>Virulence</p> Signup and view all the answers

    The term: Not harmful to the host best describes

    <p>Avirulent</p> Signup and view all the answers

    Virulence is not an absolute property of a virus, but depends on many variables. What are the three main variables?

    <p>Virus, Virulence and Host</p> Signup and view all the answers

    Which of the following variables contribute to the "tug of war" for Virulence?

    <p>A and C</p> Signup and view all the answers

    Which of the following are variables pertaining to the host that contributes to virulence?

    <p>All of the above</p> Signup and view all the answers

    An enveloped virus only has a capsid

    <p>False</p> Signup and view all the answers

    What is the chemical composition of a virus?

    <p>Double and single stranded DNA and RNA</p> Signup and view all the answers

    A virus can be visualized using compound microscopy

    <p>False</p> Signup and view all the answers

    What methods can be used during diagnosis and detection of a viral disease?

    <p>Histopathology, Necropsy, Culture/Isolation, Serology, Electron Microscopy, ELISA, RT-PCR/PCR, Clinical Signs, and Egg innoculation</p> Signup and view all the answers

    Two viruses are running rampant in a susceptible population. Virus 1 has a LD50 of 120 and Virus B has an LD50 of 60. Which one is more virulent?

    <p>LD50 of 60</p> Signup and view all the answers

    What type of viremia occurs when the virus has replicated within organs and then re-entered circulation?

    <p>Secondary Viremia</p> Signup and view all the answers

    What is the name of the host defense mechanism that results in cell lysis but NO spread of virus?

    <p>Apoptosis</p> Signup and view all the answers

    Viruses are capable of breaching the skin in order to enter the host

    <p>False</p> Signup and view all the answers

    If a virus is incapable of breaching the skin, how does it enter the host skin?

    <p>It enters through a cut or breach</p> Signup and view all the answers

    Which of the following is NOT a route of entry of viruses into host-skin?

    <p>All of the above are a route of entry</p> Signup and view all the answers

    Which of the following is not a route of entry of viruses into Host-Mucous membrane?

    <p>Contaminated Needle</p> Signup and view all the answers

    What is a common route of entry of a virus into the host's GI tract?

    <p>Via contaminated food and water</p> Signup and view all the answers

    List the common sites of pathogenesis and virulence for the Respiratory tract.

    <p>Sites include the nasal cavity, pharynx, larynx, trachea, primary bronchi and lungs</p> Signup and view all the answers

    A local spread of a virus on epithelial surfaces can cause what, respectively?

    <p>Can cause localized infections that may or may not proceed to subepithelial layer/underlying tissues</p> Signup and view all the answers

    What should the virus do to reach the subepithelial layer/underlying tissues from epithelial surfaces?

    <p>Should overcome host defenses</p> Signup and view all the answers

    What type of virus is known to cause cancer?

    <p>Oncoviruses</p> Signup and view all the answers

    If the virus is successful in reaching the subepithelial layer/underlying tissues, the virus has access to ______, ______, and _______.

    <p>Lymphatics, phagocytic cells and tissue fluids</p> Signup and view all the answers

    The presence of virus in the blood is known as

    <p>Viremia</p> Signup and view all the answers

    The initial entry of the virus into the blood is known as

    <p>Primary viremia</p> Signup and view all the answers

    What are the two ways primary viremia can occur?

    <p>A and C</p> Signup and view all the answers

    The virus has replicated/multiplied in major organs and once more, entered the circulation is describing:

    <p>Seconday Viremia</p> Signup and view all the answers

    Infection that spreads beyond the primary site of infection is known as

    <p>Disseminated infection</p> Signup and view all the answers

    If a number of organs or tissues are infected, this is describing what type of infection?

    <p>Systemic infection</p> Signup and view all the answers

    What are the ways that a virus can spread via nerves in the host?

    <p>All the above</p> Signup and view all the answers

    Per the previous question regarding different ways a virus can spread via nerves, what is the fourth way a virus can spread?

    <p>Virus can cross blood brain barrier and infect CNS</p> Signup and view all the answers

    Viruses that can enter the CNS after infection of a peripheral site diescribes what type of virus?

    <p>Neuroinvasive virus</p> Signup and view all the answers

    Viruses that can infect neural cells are known as what type of virus?

    <p>Neurotropic</p> Signup and view all the answers

    Viruses that can cause disease of nervous tissue, manifested by neurological symptoms and often death, describes what type of virus?

    <p>Neurovirulent</p> Signup and view all the answers

    Define Tropism

    <p>The affinity of a virus for a particular host tissue</p> Signup and view all the answers

    Define Pantropic Viruses

    <p>Viruses can replicate in more than one host tissue/organ</p> Signup and view all the answers

    What are the 5 general outcomes of viral injury?

    <p>Cell lysis/bursting, Apoptosis, Immunosuppression, oncoviruses, persistent infection</p> Signup and view all the answers

    This outcome of viral injury happens following replication, allowing the release of new viruses

    <p>Bursting/Cell lysis</p> Signup and view all the answers

    _________ of infectious viriuns is crucial to the maintenance of infection in populations

    <p>Shedding</p> Signup and view all the answers

    This type of infection is usually involves intensive shedding over a short time period

    <p>Acute infection</p> Signup and view all the answers

    This type of infection can be shed at lower titers for months to years.

    <p>Persistent</p> Signup and view all the answers

    Match the following to the correct description.

    <p>Vesicle = Fluid filled sac/small distince elevation with fluid Ulcer = Opening of the skin caused byu sloughing of necrotic tissue Nodule/tumor = Solid tumorous mass Warts = Benign skin growths that appear when a virus infects top layer of skin</p> Signup and view all the answers

    Match the following to correct description

    <p>Disseminated intravascular coagulation (DIC) = Clots that form throughout body followed by hemorrhages Teratogenic viruses = Cause developmental defects of embryo or fetus after in utero infection Damage to endothelium = Hemorrhages (pin-point/small spots); Ecchymoses Inflammed bronchus = Lumen of bronchus is narrowed b/c of inflammation and exudation</p> Signup and view all the answers

    What consequence of systemic viral infections resulsts in a reddining of the skin?

    <p>Erythema</p> Signup and view all the answers

    Study Notes

    Virulence and Pathogenesis

    • The ability of a virus to cause disease in a host is referred to as pathogenicity.
    • The virus that causes disease is called a pathogen.
    • The manner of development of a disease is called pathogenesis.
    • The term virulence is used as a quantitative or relative measure of the degree of pathogenicity of the infecting virus.
    • Virulence is not an absolute property of a virus, but depends on many variables.

    Variables of Virulence

    • The three main variables of virulence are the virus, the host, and the environment.
    • The "tug of war" for virulence involves the interaction between the virus and the host's immune system.
    • Variables pertaining to the host that contribute to virulence include the host's immune response, age, and nutrition.

    Viral Structure and Composition

    • An enveloped virus has a capsid and a lipid envelope.
    • The chemical composition of a virus includes nucleic acid (DNA or RNA) and protein.
    • A virus can be visualized using electron microscopy, not compound microscopy.

    Diagnosis and Detection

    • Methods used during diagnosis and detection of a viral disease include virus isolation, serology, and molecular biology techniques.

    Virulence and Viremia

    • Virulence is measured by the LD50 (the dose of virus required to kill 50% of infected animals).
    • Virus 1 with an LD50 of 120 is less virulent than Virus B with an LD50 of 60.
    • Viremia occurs when the virus has replicated within organs and then re-entered circulation.
    • The name of the host defense mechanism that results in cell lysis but no spread of virus is apoptosis.

    Routes of Entry

    • Viruses can breach the skin or enter through mucous membranes, respiratory tract, or GI tract.
    • If a virus is incapable of breaching the skin, it can enter through cuts, wounds, or insect vectors.
    • The route of entry of viruses into the host's GI tract is through ingestion of contaminated food or water.
    • Common sites of pathogenesis and virulence for the Respiratory tract include the nose, throat, and lungs.

    Local Spread and Systemic Infection

    • A local spread of a virus on epithelial surfaces can cause lesions, inflammation, and cell death.
    • To reach the subepithelial layer/underlying tissues, the virus must penetrate the epithelial barrier.
    • If the virus is successful in reaching the subepithelial layer/underlying tissues, it has access to blood, lymph, and nerves.
    • The presence of virus in the blood is known as viremia.
    • The initial entry of the virus into the blood is known as primary viremia.
    • Primary viremia can occur through direct entry of the virus into the blood or through replication in infected organs.
    • Infection that spreads beyond the primary site of infection is known as systemic infection.
    • If a number of organs or tissues are infected, this is describing a disseminated infection.

    Viral Spread and Neurotropism

    • Viruses can spread via nerves in the host through retrograde axonal transport, anterograde axonal transport, or transsynaptic transmission.
    • The fourth way a virus can spread via nerves is through neuronal cell-to-cell transmission.
    • Viruses that can enter the CNS after infection of a peripheral site are known as neurotropic viruses.
    • Viruses that can infect neural cells are known as neurovirulent viruses.
    • Viruses that can cause disease of nervous tissue, manifested by neurological symptoms and often death, are known as neuropathogenic viruses.

    Tropism and Outcomes

    • Tropism refers to the specific infectivity of a virus for certain cells or tissues.
    • Pantropic viruses are capable of infecting a wide range of cells or tissues.
    • The 5 general outcomes of viral injury are latency, chronic infection, resolution, transformation, and death.
    • The shedding of infectious virions is crucial to the maintenance of infection in populations.
    • Acute infection usually involves intensive shedding over a short time period.
    • Chronic infection can be shed at lower titers for months to years.

    Consequences of Systemic Infections

    • One consequence of systemic viral infections is a reddening of the skin, known as erythema.

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    Description

    This quiz covers the concept of viral pathogenesis, which is the ability of a virus to cause disease in a host. It's an important concept in microbiology and immunology. Test your knowledge and learn more about viral pathogenesis.

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