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RUSVM Principles Of Infectious Diseases > Week 2 + 3 > Flashcards

Week 2 + 3 Flashcards

1
Q

T/F: Chain of infection occurs in the following order:

Agent > Reservoir > Portal of Entry > Mode of Transmission > Portal of Exit > Susceptible Host > Agent

A

False; Agent > Reservoir > Portal of Exit > Mode of Transmission > Portal of Entry > Susceptible Host > Agent

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2
Q

Define exposure

A

Introduction of a new pathogen into a susceptible population

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3
Q

T/F: Contact always ends with transmission

A

False; contact does not always = transmission

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4
Q

What is the adoption, establishment,and dissemination of a pathogen in the susceptible population? What does it require?

A

Transmission; a adaptable pathogen that can travel between hosts

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5
Q

Label the arrows:

Reservoir population ———> susceptible population ———> disease epidemic

A

Exposure, transmission

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6
Q

What is a reservoir?

A

A habitat or population in which infectious agent normally lives, grows, and multiplies over time

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7
Q

T/F: Animal reservoirs are always ill

A

False; not necessarily, can be asymptomatic “carrier”

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8
Q

T/F: All sick animals are reservoirs

A

False

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9
Q

T/F: A reservoir does not die

A

False; The individual can be killed while the population maintains the agent (ex: rabies)

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10
Q

What is a method a pathogen uses to leave a host body? What are some examples?

A

Portal of exit

-saliva, blood, feces, urine,etc.

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11
Q

What are the two main modes of transmission?

A

Vertical and Horizontal

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12
Q

What mode of transmission goes from mother to offspring?

A

Vertical

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13
Q

What are the types of vertical transmission and their features?

A

Transplacental/at fecundation/egg development
- virus infects in utero, through placenta
- virus attaches to to spermatozoa or oocyte. “pre-infected”
- the more protects n the placenta (layers),the harder it is for virus to get in (less even easier in humans, more defense in horses)

Transovarial
- passage of pathogen from adult female to eggs through ovaries of arthropod

Perinatal
- “surrounding birth”
- at parturition (HIV, enzootic bovine leucosis)
- or through colostrum/milk

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14
Q

What are the types of horizontal transmission and their features?

A

Direct
- limited space
- NO intermediary
- short time period
- directly from reservoir to susceptible host .
Ex: bites, coughing

Indirect
- distance
- intermediary
- longer time period
- via any sort of intermediary, either animate or inanimate
Ex: touching infected handle, using a used cup

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15
Q

What are the types of direct horizontal transmission and their features?

A

Contact
- skin (ex: ringworm)
- mucous membranes (ex: sexual transmission, saliva)
- brutal (ex: biting)

Droplet/Airborne
- droplet; wet, large, short range aerosols (ex: sneezing, coughing)
- airborne; disease agents don’t survive long within aerosolized particles
*waterborne; aquatic animals only, through gills

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16
Q

What are the kinds of indirect horizontal transmission?

A

Vehicle - inanimate object serving to communicate disease
Vector - arthropods who carry and transmit pathogens

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17
Q

What are the types of vehicles? What type of transmission is it?

A

Common
- water, food, soil

Fomite
- objects that can be contaminated and transmit disease on a limited scale

  • Indirect horizontal transmission
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18
Q

What are the types of vectors? What type of transmission is it?

A

Mechanical
- animal that carries a pathogen between hosts without getting infected itself

Biological
- pathogen undergoes changes or multiples while in vector

  • Indirect horizontal transmission
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19
Q

What is portal of entry?

A

Method a pathogen uses to enter the body of the susceptible host

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20
Q

T/F: Most pathogens can go through skin, this is the most efficient portal of entry

A

False; skin is well protected, most efficient portal of entry is eyes.

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21
Q

What is a member of the population who is at risk of becoming infected?

A

Susceptible host

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22
Q

What is the composition of a nucleotide?

A

A nitrogenous base, five-carbon sugar (ribose or deoxyribose) and up to three phosphate groups

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23
Q

What are purines? Pyrimidines?

A

Purines - two joined carbon rings w/ five or six members
- Adenine (A), Guanine (G)

Pyrimidines - six carbon ring
- Cytosine (C), Thymine (T), Uracil (U)

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24
Q

What is a nucleoside?

A

A Base + a purine or pyrimidine

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25
Q

What is the central dogma of genetic information?

A

DNA —(transcription/reverse transcription)—> RNA —(translation)—> Protein

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26
Q

T/F: DNA replication is semi conservative, ie: a parental strand and a daughter strand in a new molecule

A

True

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27
Q

Compare transcription in prokaryotic and eukaryotic cells

A

Prokaryotic:
- single rna polymerase
- no introns
- polycistronic
- no polyadenylation
- no 5’ cap

Eukaryotic
- rna polymerase i, ii, iii
- introns removed
- monocistronic
- polyadenylation at 3’ end
- methylated cap at 5’ end

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28
Q

Describe translation in bacteria

A

DNA strand with RNA polymerase interspersed along it, ribosome hanging off on strands of mRNA. Direction of translation up the mRNA strands towards the DNA

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29
Q

What are the type of mutations?

A

Silent, missense, nonsense, frameshift

30
Q

What is silent mutation?

A

Mutation of DNA sequence without apparent effect. Base change in DNA, no change in amino acid

31
Q

What is a missense mutation?

A

A change in a codon, that changes the amino acid, which changes the protein function

32
Q

What is a nonsense mutation?

A

Change in a coding codon to a termination (stop) codon, resulting in premature termination

33
Q

What is a frameshift mutation?

A

Deletion or addition of a number of base pairs other than a multiple of three

34
Q

How does genetic transfer in bacteria function?

A

-Acquisition of new genetic markers by incorporation of added DNA from either the environment or other bacteria/substances

Conjunction: “mating” of two bacteria with transfer of genetic material
Transduction: transfer of genetic material between bacteria via phage
Transposition: movement of transponder to a new site in the genome

35
Q

Define virology:

A

Study of viruses ad viral diseases

36
Q

T/F: A virus is a non-living entity

A

True

37
Q

T/F: viruses contain nucleic acid genome (DNA or RNA) surrounded by a protein coat (Capsid), sometimes a lipid envelope, and cellular organelles

A

False; no organelles

38
Q

Why are viruses like obligate intracellular parasites?

A
  • inert/dormant particles outside of cell
  • hijacker’s an utilize host cell machinery to produce proteins and nucleic acid for next generation
  • cannot multiply by division, so various parts of virus come together from different parts of host cell
39
Q

T/F: A capsomere is made of multiple capsids

A

False; A capsid is made of multiple capsomeres held together by non-covalent bonds. The capsid is the protein shell of a virus that encases the nucleic acid or genome. The capsid + genome is a nucleocapsid.

40
Q

What are some features of a lipid envelope?

A
  • additional layer covering capsid
  • usually a lipid bilayer derived from host cell
  • glycoprotein “spikes” present on surface
  • naked viruses have no envelope
  • enveloped viruses have the additional lipid layer
41
Q

What is pleomorphism?

A

The ability of some viruses to alter their size and shape

42
Q

What is the order of events in replication?

A

Attachment > penetration > uncoating > synthesis of viral nucleic acids and protein > assembly and maturation > release in large numbers

43
Q

What are impacts of virus replication on the cell?

A
  • cell death (lysis (explosion), alteration of cell membrane, apoptosis (cell suicide))
  • fusion of cells (multinucleated, hybrids)
  • no apparent change (latent, persistent, chronic infection)
  • transformation (cell becomes malignant)
44
Q

T/F: the ability of a virus to cause disease in a host is virulence

A

False; Pathogenicity. A pathogen is a virus that causes disease

45
Q

Define pathogenesis

A

Manner or mechanism of development of a disease

46
Q

Define virulence

A

A quantitative measure of the degree of pathogenicity of the infecting virus

47
Q

T/F: A virus that does not cause disease is avirulent, a virus that is not harmful to the host is non-pathogenic

A

False; A virus that does not cause disease is non-pathogenic, a virus that is not harmful to the host is avirulent

48
Q

Virulence is variable dependent. What are some factors that influence virulence?

A

Virus
- genetic variation
- route of entry
- affinity
- dose of infection
- immuno evasion

Host
- species
- immunity
- physiological factors
- fever

Other
- environment
- dual infections

49
Q

T/F: A higher LD50 (Lethal dose 50) is more lethal

A

False; a lower dose means it takes less of the virus to cause death in 50% of the population

50
Q

What are the sequential steps of pathogenesis?

A

Entry of virus and primary replication > spread and infection of target organs > virus-cell interactions > tissue/organ injury > shedding > trophy (increase in viral members) > host casualty

51
Q

What are routes of entry of viruses into host?

A
  • Transcutaneous injection (bite of arthropod, bite of infected animal, contaminated objects (ex: dirty needle))
  • Mucous membranes (conjunctiva, respiratory tract, urogenital tract)
  • GI tract (virus in contaminated food/H2O)
  • Scratch/cut/breach in skin
52
Q

What is the direction of viral spread?

A

Epithelium > Subepithelial layer/underlying tissues/lymphatics > blood vessels

53
Q

How does spread of virus in epithelium proceed?

A
  • local spread on epithelial surfaces
  • cause localized infection
  • may/may not proceed to subepithelial (must overcome local host defense)
54
Q

T/F: Subepithelial invasion can help carry virus to the bloodstream, resulting in viremia: the presence of virus in blood

A

True

55
Q

What are the two phases of viremia? What are their particularities?

A

Primary viremia: initial entry of virus into the blood
Two methods:
- spread of virus infection to blood from subepithelial tissue
- directly injected into blood, through bite of mosquitoes or dirty syringes

Secondary viremia: virus replicated/multiplied in major organs and then reentered the bloodstream

56
Q

T/F: Disseminated infection is when infection spreads beyond the primary site, systemic infection is when multiple organs/tissues are infected

A

True

57
Q

What are methods a virus can infect the central nervous system?

A
  • through peripheral nerves (ex: rabies)
  • through receptor neurons in the nasal olfactory epithelium (ex: HSV-1)
  • cross the blood-brain barrier via monocytes (ex: west nile)
58
Q

Define neurotrophic virus

A

Viruses that can infect neural cells, either by neural or hematogenous spread

59
Q

A virus that cause disease of nervous tissue, manifested by neurological symptoms an often death is a ____________.

A virus that enters the CNS after infection of a peripheral site is __________.

A

Neurovirulent virus, Neuroinvasive virus

60
Q

Define tropism. What does pantropic mean?

A

Specificity/affinity of virus for particular host tissue
Ex: enteric viru replicates in gut but not in lungs

A virus that can replicate in more than one host organ

61
Q

What are some mechanisms of viral injury?

A
  • inhibition of host-cell nucleic acid synthesis
  • inhibition of host-cell RNA synthesis (transcription)
  • inhibition of host-cell protein synthesis
  • cytopathic effects of “toxic” viral proteins
  • interference with Elul are membrane function
62
Q

What are the possible outcomes of viral injury and some features?

A
  • cell lysis/bursting (follows replication, releases new viruses)
  • apoptosis (programmed cell death, last resort to prevent virus reproduction)
  • oncoviruses (cancer causing, ex: retrovirus, papillomavirus)
  • persistent infection
  • immunosuppression
63
Q

Why is virus shedding important?

A

Crucial to maintenance of infection in a population, amount of virus shed is important in relation to disease transmission.

64
Q

T/F: Acute infection causes shedding at lower titers over a short time period, persistent infection causes intensive shedding over months or years

A

False; Acute infection causes intensive shedding over a short time period, persistent infection causes shedding at lower titers over months or years

65
Q

What are routes of viral shedding?

A
  • oropharynx and GI tract
  • respiratory tract
  • mucous membranes, oral and genital fluids
  • blood, urine, milk
  • skin
66
Q

T/F: vesicles, ulcers, nodules, warts, and erythema are all examples of viral injury to the skin

A

True

67
Q

Describe the types of viral injury to skin

A

**can be localized or disseminated

Vesicle
- small distinct elevation with fluid

Ulcer
- opening in skin caused by sloughing of necrotic tissue,extending past epidermis

Nodule (tumor)
- palpable, solid, elevated mass. Doubles with distinct borders, tumors extending deep into dermis

Warts
- benign growth on the top layer

Erythema
- reddening of skin

68
Q

What are examples of viral injury to the GI system and respiratory system?

A
  • blunting/fusion of intestinal villi, villus atrophy, diarrhea
  • inflammation of the airways
69
Q

What are examples of viral injury to the CNS?

A
  • lytic infection of neurons
  • neuronal necrosis
  • neuronophagia (devouring of neuronal cells by phages)
  • perivascular cuffing
  • progressive demyelination
  • neuronal vacuolation (prion disease)
70
Q

T/F: hemorrhages are an example of viral injury to the cardiovascular system

A

False; hemopoietic system

71
Q

Viral infection of a fetus can cause ______

A

Developmental defects of the embryo (ex: porencephaly, hydraencephaly)

72
Q

What are some viral immune-evasion methods?

A
  • negative cytokine regulation
  • alterations in antigen processing pathways
  • evasion of natural killer cells
  • alterations in B cell system
  • alterations in T cell system
  • latency
  • inhibition of apoptosis

RUSVM Principles Of Infectious Diseases (6 decks)

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