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BDS2 - BAMS > Transmission of Infection > Flashcards

Transmission of Infection Flashcards

1
Q

what are the basic principles of the chain of infection?

A
  • Infectious agent
  • Reservoirs
  • Portal of exit
  • Means of transmission
  • Portal of entry
  • Susceptible host
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2
Q

what does virulence mean?

A

ability of the microbe to cause disease

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3
Q

what does dose mean?

A

number of microbes entering the body

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4
Q

what factors are included with regards to virulence?

A

• Exotoxins
○ P.gingivalis (protease)
○ S.aureus (endotoxin & leukocidin)

• Endotoxins
○ Lipopolysaccharide
(P.gingivalis & E.coli)

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5
Q

dont know how to question this / how to understand it but here we are to learn x

A

infectious dose:
Usually expressed as infectious dose 50 (ID50)
• TB = 1 bacillus
• Syphilis = 57 bacteria (ID50)
• E.coli 0157 = <10 cfu
•Influenza virus = <10 (tissue culture ID50)

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6
Q

name reservoirs where microbes can live

A
  • humans
  • animals
  • fomites
  • environmental
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7
Q

where does most pathogenic microbes that infect humans come from?

A

other humans

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8
Q

give an example of a human pathogen that comes from animals

A

anthrax

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9
Q

give an example of a human pathogen that originates in the environment

A

clostridium tetani spores in soil

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10
Q

what are fomites

A

Contaminated objects or surfaces
Usually act as a bridge between health care workers and patients
Eg phone, keyboard, medical equipment surfaces, house keeping surfaces

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11
Q

what are the different sources of infection?

A

> patients in the acute phase of an infection = easily recognised eg influenza, common cold

> patients in the podromal phase of an infection = not easily recognised eg measles, mumps, chickenpox

> healthy carriers of pathogenic organisms = not easily recognised includes convalescent carriers and asymptomatic carriers eg HIV, Hep B and C, herpes viruses

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12
Q

what is the incubation period

A

the time between contamination and the development of symptoms
varies widely for different infections

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13
Q

what is the problem with longer incubation periods

A

longer time periods when the infecting microbe may be spread to others
means a greater spread of the disease because of more human contact

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14
Q

define asymptomatic carrier

A

an infected person with no clinical evidence of disease, though signs and symptoms of the disease may have been evident earlier

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15
Q

why are carriers dangerous in the spread of diseases

A

they are usually unaware of their infectious state

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16
Q

define colonisation

A

is the presence of bacteria on a body surface (like on the skin, mouth, intestines etc) with growth and multiplication without causing disease (clinical expression of the infection) in the person

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17
Q

define infection

A

the invasion of a host organism’s bodily tissues by disease causing organisms

18
Q

define exogenous

A

growing or originating outside an organism

caused by microbes from external soruces eg influenza

19
Q

define endogenous

A

growing or originating within an organism
caused by members of the normal flora if
- flora becomes ecologically harmful due to population / gene expression shifts eg periodontal disease, dental caries
- they become displaced to another body site or are allowed to invade deeper tissues eg post surgical infections

20
Q

explain portal of exit

A

microbes must escape from the source to colonise a new host

21
Q

what are the different modes of escape (portal of exit)

A

natural

  • coughing
  • sneezing
  • tears
  • urine

artificial

  • blood donation
  • dental handpiece aerosols
22
Q

classify pathogens in the 4 hazard groups

A
  • ability to cause infection
  • severity of the disease that may result
  • risk of population spread
  • vaccine and treatment availability
    (venn diagram - where these 4 things over lap = extremes = ebola outbreak)
23
Q

what is R0

A

the number of cases one case generates on average over the course of its infectious period

24
Q

explain R0 < 1

A

infection will die out in the long run

25
Q

explain R0 > 1

A

infection will be able to spread in a population

higher R0 number = bigger the risk there is of an infection

26
Q

what factors affect R0

A
  • duration of infectivity
  • infectiousness
  • number of susceptible people
27
Q

what is influenza

A 
infectious agent
RNA virus with segmented genome 
3 types = A, B, C
types A and B cause major outbreaks 
> X2 surface glycoproteins
- hemaglutinin H1-15
- neuraminidase N1-9
28
Q

what is pathophysiology

A

the disordered physiological processes associated with disease or injury

29
Q

what is the pathophysiology of the influenza virus

A

infection of upper and lower respirator tract

release of cytokines (IF and TNF) = fever, headache, fatigue

30
Q

explain the infection of influenza

A

uncomplicated

  • fever
  • cough
  • headaches
  • fatigue

complicated

  • bacterial pneumonia
  • ear and sinus infections
  • worsening of chronic medical conditions like asthma and heart disease
31
Q

what is the incubation period for influenza

A

2-3 days

infectious as soon as symptoms appear

32
Q

how is the influenza virus shed

A

in respiratory tract secretions

33
Q

what is the infectious period of influenza

A

3-5 days
children are infectious for longer
not everyone who is infected has obvious symptoms - could be carriers

34
Q

what is the reservoir for the influenza virus

A

humans

animals (birds carry the RNA for the disease but pigs jumble the RNA strains together and create new RNA strains)

35
Q

what is the portal of exit for the influenza virus

A

large particles

  • greater than 10 micrometres
  • droplet
  • respiratory secretions
  • contaminate surfaces

small particles

  • smaller than 10 micrometres
  • aerosol
  • respiratory secretions
  • can remain / circulate the air for mins / hours
36
Q

how long can influenza A and B survive in different surfaces

A

steel and plastic = 23-48 hours

cloth, paper and tissues = less than 8-12 hours

37
Q

what is the transmission for influenza

A

steel to hands over 24 hours
paper tissue to hands for 15mins
survives 5 mins on hands

38
Q

wha tis the portal of entry for influenza

A
  • respiration (aerosols)
  • inhalation (all particles)
  • direct contact (droplets)
  • in-direct contact (settled particles - face touching)
39
Q

who are susceptible hosts to influenza

A
  • elderly
  • young children
  • pregnancy
  • chronic medical conditions
    > diabetes
    > asthma
    > heart disease

patients with health conditions are 18 times more likely to die from having the flu

40
Q

what is the best way to prevent flu

A

get vaccinated each season

41
Q

what are the most common strains of influenza circulating

A

2 circulating A stains and 1 circulating B strain
people who design the vaccination try and predict the strains that are going to be a problem by studying flu in the other hemisphere

BDS2 - BAMS (18 decks)

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