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DWT > Virology 2: Epidemiology and transmission of Viral Diseases > Flashcards

Virology 2: Epidemiology and transmission of Viral Diseases Flashcards

1
Q

Define viral epidemiology. List the three terms used to describe.

A

Disease in population that develops before recognition of causative agents.
1. Endemic
2. Epidemic
3. Pandemic

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2
Q

Define endemic

A

Multiple/continuous transmission in a population/region/time

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3
Q

Define epidemic

A

widespread occurrence of an infectious disease in a community at a particular time. Exceeding the endemic baseline.

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4
Q

Define Pandemic

A

Worldwide epidemic

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5
Q

Define rate and how to calculate

A

Disease in a population.
Number of cases/population

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6
Q

Define Incidence or “attack rate” and how to calculate

A
  • Case to population ratio.
  • Number of cases/Population over a period of time (i.e person-years)
  • Acute/Short-duration diseases will have incidence
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7
Q

Parameters that define incidence in acute diseases

A

Three in acute disease (short-duration)
1. Proportion of the population which is susceptible (S/P)
2. Proportion of the infected susceptible individuals (I/S)
3. Proportion of the diseased infected individuals (C/I)

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8
Q

Attack Rate VS Incidence parameters

A

See image. The Parameters allow you to more clearly identify the incidence and rate among a specified population.

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9
Q

Parameters that define incidence in viral diseases

A
  1. Case/infection ratio: proportion of infections resulting in clinical disease
  2. Case/fatality ratio: proportion of infection resulting in lethal disease
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10
Q

Define Prevalence and how to calculate

A

“Picture” of disease.
- Onset of unknown date so no time parameters.
- Number of current cases/population.
- Chronic, long duration diseases

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11
Q

Characteristics of data regarding epidemiology

A

Difficult to acquire, Often incomplete and inaccurate, Easier to compute.

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12
Q

Surveillance of disease

A

Continuous reporting and monitoring for growth of data

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13
Q

Serological survey definition

A

Antibody data; subjects were clinical disease silent (No clinical signs).

Not informative for current infection rate

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14
Q

what are prospective studies?

A

tracking events that are supposed to happen in the future. (i.e: placebo and treatment groups)

*Expensive

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15
Q

What are characteristics of retrospective studies?

A

Tracking past events, only need a limited number of subjects
*cost effective

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16
Q

Steps through viral infection of an individual

A

Incubation period, Generation time, period of infectivity, infection

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17
Q

When is the incubation period?

A

Moment of infection to onset of clinical signs

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18
Q

When is the generation time?

A

From moment of infection to first day of shedding virus. Usually shorter than incubation period.

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19
Q

When is the period of infectivity?

A

First day of shedding to last day of shedding. Influences spread of disease.

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20
Q

What are characteristics of a chronic viral disease and steps through the viral lifespan?

A

Distinction between each period is difficult to asses.
-Little correlation among disease, generation time, infectivity.

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21
Q

Modes of transmission by viruses

A

Horizontal
Vertical
Zoonotic
Vector-borne
Iatrogenic
Nosocomial

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22
Q

What is Horizontal Transmission and types of contact?

A

With or without a vector and between same or different species.
- Direct contact
- Indirect contact
- Airborne

23
Q

Airborne examples

A

Droplets, aresols.

24
Q

Indirect contact example and what type of virus is usually spread?

A

Indirect contact: Fomites, easting, bedding, vehicles, needles. Usually non-enveloped viruses.
— Common vehicles: Water, feed

25
Q

Direct contact example and what type of virus is usually spread?

A

licking, rubbing, biting, sexual. Usually spreads enveloped viruses.

26
Q

Vertical Transmission and examples

A

Movement of virus from parents to offspring.
- Gestation via placenta, milking
- Germ-line transmission

27
Q

What is Germ-line transmission?

A

Type of vertical transmission. Virus is integrates into the genome of an ovum, transcription and replication of virus occurs in offspring. Creates generational infection.

28
Q

What is Arthropod Vector-Borne (Arbovirus) Transmission? What are the types? Example?

A

Uses Biological vector or Mechanical vector.

Example: Ticks, mosquitoes, sandflies

29
Q

What happens in a Biological vector?

A

Vector-borne transmission:
Virus replicates and magnifies in the vectors = Efficient transmission

30
Q

What happens in a Mechanical Vector?

A

Vector-borne transmission:
Virus DOES NOT replicate in vectors = NOT efficient at transmission

31
Q

What is Zoonotic transmission? What is the rate?

A

Viral disease transmissible from animals to humans under natural condition.

pigs closely related and many zoonotic disease
58% of recognized human diseases are zoonotic (and rising)

32
Q

What is Iatrogenic transmission? Example?

A

Patient to patient transmission under veterinary care during interaction of vets to animals -Preventable with biosecurity

Ex: Reusing needles on beef farm

33
Q

What is Nosocomial transmission? Example?

A

Transmission occurs while the animals are in the hospital - Preventable

Ex: Sterilizing surgery tools properly

34
Q

Types of Viral Infections

A

Acute infection, Persistent infection, Chronic infection, Latent infection, Recrudescence, Productive, abortive, restrictive, transforming

35
Q

What is Acute infection? How long does it last?

A

Rapid production of infectious viruses, Rapid resolution and elimination.
- A few days
- May not produce disease

36
Q

What is persistent infection? How long does it last?

A

Infection is not cleared efficiently, Virus particles are produced for a long time.
-Months or Years
-Two types: Chronic, Latent

37
Q

What is chronic Infection?

A

Persistent infections that will eventually cleared

38
Q

What is latent infection? What are the steps?

A
  1. Viral genome is integrated into the cellar genome of host but is not expressed.
    - No infectious expression
  2. Under stress animal will undergo recrudescence
    -New infectious virus expression
39
Q

What is recrudescence? What type of infection does it correlate with?

A

Activation of latency due to many reasons
- I.E: immunosuppression, stress.
-New infection expression causing disease fair-up and new immune response

40
Q

What are patterns of viral shedding? Systemic vs local infectious shedding?
What does shedding determine?

A

-Shed through body openings and surfaces.
-Local infections shed locally.
-Systemic infections will have various routes of shedding.
-Amount of shedding defines infection outcome.

41
Q

What is shedding? How does this impact virus survival?

A

Replication of Virus
Last phase of viral pathogenesis, mandatory for the virus to survive in the host.
** Not all shed (i.e: retrovirus = germ-line)

42
Q

Routes of shedding?

A

Skin
Respiratory
Saliva
Feces
Genital secretions
Urine
Milk

43
Q

Shedding: Skin

A

Route of shedding
Not a major route.
Contact, abrasions, wounds

44
Q

Shedding: Respiratory

A

Route of shedding
VERY important
- Local and systemic
- Shedding will occur before, during, and after clinical signs

45
Q

Shedding: Saliva

A

Route of shedding
Salivary gland/oral cavity
i.e Rabies, FIV

46
Q

Shedding: Feces

A

Route of shedding
GI tract viruses
** Can occur without GI clinical signs

47
Q

Shedding: Genital secretions

A

Route of shedding
Sexual activity, semen, mucus

48
Q

Shedding: Urine

A

Route of shedding
Viruses from kidneys
Hantavirus: mice to humans

49
Q

Shedding: Milk

A

Route of shedding
NOT important
Mammary gland replication

50
Q

What is and what determines host range?

A

Host cells determining ability of viral transmission.
- Receptors on animal tissues/cells. - Susceptibility and permissively.

51
Q

What is susceptibility?

A

Ability of host to become infected.

52
Q

What is permissivity?

A

Ability of virus to replicate and produce progeny(offspring) viruses

53
Q

Host factors determining the outcome of infection

A

Age, Sex, Reproductive status of population, immune status of population, nutritional status of population, genetics of population

DWT (28 decks)

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