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FCPH > dynamic of disease transmissionn part 1 > Flashcards

dynamic of disease transmissionn part 1 Flashcards

1
Q

what is a communicable disease ?

A

a disease that is caused by a transmission of a specific pathogenic agent to a susceptible host

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2
Q

what is the epidemiological triad ?

A

agent
host
environment

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3
Q

what are the components of the chain of infection ?

A

infectious agent leaves a host or a reservoir
through a portal of exit
and enters a susceptible host through a portal of entry

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4
Q

what are the factors that can describe an agent ?

A 
infectivity 
infectiousness 
virulence 
pathogenicity 
infectious dose
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5
Q

how is infectivity measured ?

A

measured by the ratio of the number of people who become infected to the total number exposed to the agent

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6
Q

how is the infectiousness measures ?

A

by the basic reproduction number R0

and effective reproductive number

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7
Q

what is the basic reproduction number ?

A

it is the avergae number of secondary infections produced by a typical case of an infection in a population where everyone is susceptible

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8
Q

inn general for an epidemic to occur what is the R0 of a totally susceptible population ?

A

R0 must be more than 1 for an epidemic to occur in this case

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9
Q

what is the effective reproductive number ?

A

average number of secondary cases per infectious case in a population made up of both susceptible and non susceptible hosts

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10
Q

what conclusions can be drawn from different results and values of the effective reproductive number ?

A

R>1 the number of cases will increase
R=1 the disease is endemic
R<1 there will be a decline in cases

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11
Q

how can the effective reproductive number be estimated from the basic reproductive number ?

A

For example, if R0 for influenza is 12 in a population where half of the population is immune, the effective reproductive number for influenza is 12 x 0.5 = 6.

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12
Q

what value should the effective reproductive number reach inn order for herd immunity to be established ?

A

must fall below 1

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13
Q

what does the pathogenicity describe ?

A

the number of people who developed clinical symptoms in comparison to the total number of infected individuals

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14
Q

what does the virulence describe ?

A

is the ratio of the number of people with severe and fatal disease to the total number of people with disease

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15
Q

what are the type of human reservoirs ?

A

cases or carriers

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16
Q

what are the types of human cases in reservoirs ?

A

apparent and inapparent

17
Q

what are the classifications of inapparent cases ?

A

preclinical
subclinical
latent

18
Q

what are the preclinical cases ?

A

not clinically apparent but destined to progress to clinical

19
Q

what are subclinical cases ?

A

not apparent clinically and are not destined to become apparent

20
Q

how are subclinical cases identified ?

A

through serological testing or culture of the organism

21
Q

what are the features of a latent infection case ?

A

no active multiplication of the organism , but only the genetic message is present in the host

22
Q

what are the types of carriers ?

A

incubatory - shed during incubation period
contact/healthy
convalescent - shed w homa by5efo

23
Q

what are the divisions of an infectivity period ?

A

transient - days
temporary - weeks up to 3 months
chronic - more than 3 months to life

24
Q

what are zoonoses ?

A

single diseases that primarily infect and spread between animals but have the potential transmission to humans

25
Q

what are the different modes of transmission ?

A

direct transmission
indirect transmission
airborne transmission
vertical transmission n

26
Q

what is included under direct transmission ?

A

droplet transmission
direct contact
trans placental

27
Q

what is included under indirect transmission ?

A

vehicle borne

vector borne

28
Q

what is included under airborne transmission ?

A

droplet nuclei

dust

29
Q

what is included under vertical transmission ?

A

in utero
perinatal
breast feeding

30
Q

what is the incubation period ?

A

the period of time it takes for the 1st clinical sign to show after entry of the pathogen into the host

31
Q

what is the period of communicability ?

A

period where the person is contagious

FCPH (39 decks)

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