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RUSVM PID Exam 1- Black > Virulence and Pathogenicity- Virology > Flashcards

Virulence and Pathogenicity- Virology Flashcards

1
Q

Define pathogenicity.

A

The ability of a virus to cause disease in host

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2
Q

Define pathogen

A

A virus that causes disease

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3
Q

Define pathogenesis

A

The manner/mechanism of development of a disease

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4
Q

Define virulence

A

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

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5
Q

Define avirulent

A

No virulent (not harmful to the host)

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6
Q

What factors related to the host effect the virulence of a virus?

A

Species
Immunity
Physiological factors (age, nutrition status, hormones, stage of cell differentiation)
Fever

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7
Q

What factors related to the virus effect its virulence?

A 
Genetic variation of the virus
Route of entry into the host
Affinity of the virus to host organs
Dose of infection
Immuno evasion
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8
Q

What factors effect the virulence of a virus unrelated to the host or the virus itself?

A

Environment

Duel infections

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9
Q

What is used to measure virulence?

A

Lethal dose 50 (LD50) - the dose of the virus that is required to kill 50% of animals, such as mice

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10
Q

A more virulent virus would have a higher or lower LD50?

A

Lower - less is needed

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11
Q

What are the routes of entry for a virus?

A

Skin
Mucous membranes
GI Tract
Respiratory Tract

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12
Q

How does a virus penetrate the skin?

A

Cut or breach
Transcutaneous injections (bite of arthropods)
Bite of infected animal
Contaminated objects (needles, etc)

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13
Q

How does a virus penetrate the mucous membrane?

A

Conjunctiva
Oropharynx
Genitourinary Tract and Rectum

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14
Q

How does a virus penetrate the GI Tract?

A

Contaminated food or water

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15
Q

How do viruses spread in a host?

A

epithelium –> subepithelial layer/ underlying tissues, lymphatics –> blood streams –> nerves

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16
Q

How is a virus spread in the epithelium?

A

Local spread, causes localized infection, may or may not proceed to subepithelium

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17
Q

How does a virus spread from the epithelium to the subepithelium?

A

Overcome local host defense

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18
Q

How does a virus spread from the subepithelium to the blood stream?

A

The virus get access to lymphatics, phagocytic cells, and tissue fluids in the subepithelium which help carry the virus to the bloodstream.

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19
Q

Define viremia.

A

Presence of virus in the blood

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20
Q

What is primary viremia?

A

initial entry of virus into the blood

21
Q

How does primary viremia happen?

A

Spread of viral infection to blood from subepithelial tissue/ lymphatics

OR

Direct injection in blood, through bite of mosquitoes or syringes

22
Q

What is secondary viremia?

A

When a virus has replicated/multiplied in major organs and once more entered circulation

23
Q

What is disseminated infection?

A

Infection spreads beyond the primary site of infection

24
Q

Whats is systemic infection?

A

If a number of organs or tissues are infected

25
Q

How do viruses spread to the nerves?

A

Through the peripheral nerves

Through receptor neurons in the nasal olfactory epithelium

Viruses can cross blood-brain barrier and infect CNS

26
Q

Define neurotropic virus

A

Viruses that can infect neural cells, infection can occue by neural or hematogenous spread

27
Q

Define neuroinvasive virus

A

Viruses that enter the central nervous system (spinal cord and brain) after infection of peripheral site

28
Q

Define neurovirulent virus

A

Viruses that cause disease of nervous tissue, manifested by neurological symptoms and often death

29
Q

Define tropism

A

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

30
Q

Define pantropic viruses

A

can replicate in more than one host organ/tissue

31
Q

What is the mechanism of viral injury and disease?

A

Virus-cell interactions

32
Q

What are the outcomes of viral injury?

A 
Cell lysis following virus replication
Apoptosis 
Oncoviruses
Persistent Infection - viruses remain latent or dormant in host cell for long periods, escaping detection
Immunosupression
33
Q

What are oncoviruses?

A

Oncogenic viruses; viruses that cause cancer

34
Q

Define virus shedding

A

Shedding of infectious virions is crucial to the maintenance of infection in populations

35
Q

Define acute infection in terms of shedding

A

Usually intensive shedding over short period of time

36
Q

Define persistent infections in terms of shedding

A

Can be shed at lower titers for months to years

37
Q

Describe viral injuries that effect the skin.

A

Can be localized or dissminated.

Ulcer
Nodule
Wart
Erythema

38
Q

What is a vesicle on the skin?

A

fluid filled sac

39
Q

Define ulcer

A

Opening in the skin caused by sloughing of necrotic tissue, extending past the epidermis

40
Q

Define nodule

A

Solid tumorous mass

41
Q

Define warts

A

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

42
Q

Define erythema

A

reddening of the skin

43
Q

How do viruses get into the GI tract?

A

Ingestion or from the blood, systemic infection

44
Q

What happens once a virus enters the GI tract? What are the physical symptoms?

A

Intestinal enterocytes are destroyed resulting in malaabsorption and diarrhea resulting in dehydration, acidosis, and hemoconcentration

45
Q

How do viruses effect the respiratory tract?

A

inflammation
obstruction of air passages
hypoxia and respiratory distress

46
Q

What is necrosis?

A

Death of body tissue

47
Q

What is perivascular cuffing?

A

Inflammatory cells around blood vessels in CNS

48
Q

How do viruses effect the hemopoietic system?

A

damage to epithelium- blood clots form throughout body followed by hemorrhages
viral infection of the fetus- teratogenic viruses

49
Q

Define teratongenic viruses

A

Cause developmental defects of embryo or fetus after in-utero infection

RUSVM PID Exam 1- Black (6 decks)

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