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First Semester: Principles of Infectious Disease > Lecture 8: Virulence of Viruses > Flashcards

Lecture 8: Virulence of Viruses Flashcards

1
Q

Pathogenicity

A

the ability of a virus to cause disease in the host

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2
Q

Pathogen

A

The virus which causes disease

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3
Q

Pathogenesis

A

the manner/mechanism of development of a disease

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4
Q

Virulence

A

quantitative or relative measure of the degree of pathogenicity of the infecting virus

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5
Q

Avirulent

A

not harmful to the host

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6
Q

Virulence factors related to the virus

A
  • Genetic variation of virus
  • Route of entry of virus in host organs
  • Affinity of virus to host organs
  • Dose of infection
  • Immuno evasion
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7
Q

Virulence factors related to the host

A
  • Host species
  • Host immunity
  • Host physiological factors (nutrition, age, hormones, stages of cell differentiation)
  • Fever
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8
Q

Lethal dose 50 (LD50)

A

The dose of the virus required to cause death in 50% of animals

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9
Q

Three routes of entry of viruses into host-skin

A
  1. Bite of arthropods
  2. Bite of infected animal
  3. Contaminated objects
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10
Q

Three routes of entry of viruses into host-mucous membrane

A
  1. Conjunctiva
  2. Oropharynx
  3. Genitourinary tract/rectum
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11
Q

Two defenses of mucous membranes

A

IgA (antibodies)

Virucidal proteins

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12
Q

Local spread of viruses on epithelial surfaces

A
  • Causes localized infection

- May or may not proceed to subepithelial/underlying tissues

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13
Q

Subepithelial invasion

A
  • Viruses get access to lymphatics, phagocytic cells, and tissue fluids
  • Help carry virus to blood stream
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14
Q

Viremia

A

Presence of virus in blood stream

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15
Q

Primary viremia

A

Initial entry of virus into the blood

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16
Q

Two ways primary viremia may occur

A
  • Spread of virus to bloof from subepithelial tissue/lymphatics
  • Direct injection into blood stream
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17
Q

Secondary viremia

A

Virus has replicated in major organs and has once more entered circulation

18
Q

Disseminated infection

A

Spreads beyond primary site of infection

19
Q

Systemic infection

A

A number of organs or tissues are infected

20
Q

Neurotropic virus

A

Viruses that can infect neural cells. Infection may occur by neural or hematogenous spread

21
Q

Neuroinvasive virus

A

Viruses enter the CNS after injection at a peripheral site

22
Q

Neurovirulent virus

A

Cause disease of nervous tissue, manifested by neurological symptoms and often death

23
Q

How do viruses cross the blood-brain barrier

A

they hide in monocytes

24
Q

Tropism

A

The specificity/affinity of a virus for a particular host tissue

25
Q

Pantropic

A

can replicate in more than one host tissue/organ

26
Q

Cell lysis allows

A

release of new viruses

occurs after viral replication

27
Q

Apoptosis

A

Programmed cell death

Host will activate as last resort to eliminate viral factories before new virus production is complete

28
Q

Oncoviruses

A

Cause cancer

29
Q

Persistant infection

A

Remain dormant

Can cause chronic stimulation of host immune system, resulting in immunopathology

30
Q

Infectious bursal disease

A

Viral replication causes atrophy of bursa and severe deficiency of B lymphocytes, resulting in immunosuppression, causing host to become susceptible to other pathogens

31
Q

Acute infection

A

intensive shedding over a short period of time

32
Q

Persistent infection

A

Shed at lower titers for months-years

33
Q

Skin infection

A

Localized (papilloma) or disseminated (lumpy skin disease)

34
Q

Warts

A

Benign skin growths that appear when a virus infects the top layer of the skin

35
Q

Erythema

A

Reddening of ski

36
Q

Neuronophagia

A

killing of neuronal cells by phagocytic cells

37
Q

Perivascular cuffing

A

inflammatory cells around blood vessels in CNS

38
Q

Disseminated intravascular coagulation

A
  • Widespread activation of clotting mechanism that results in the formation of blood clots in small blood vessels throughout the body
  • Triggered by viral infection
  • Over time, clotting proteins in blood are used up and severe bleeding can occur
39
Q

Vasculitis

A

inflammation and damage to blood vessels

40
Q

Vasculitis can be regulated by

A

immune-complex formation

41
Q

Teratogenic viruses

A

cause developmental defects o embryo or fetus after in-utero infection

42
Q

7 viral immune-evasion strategies

A
  • Negative cytokine regulation
  • Alterations in antigen processing pathways
  • Evasion of natural killer cells
  • Alterations in the B cell system
  • Viral evasion through latency
  • Inhibition of apoptosis

First Semester: Principles of Infectious Disease (22 decks)

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