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BDS2 BAMS > Transmission of infection > Flashcards

Transmission of infection Flashcards

1
Q

What are the 6 features of the chain of infection?

A
  • Infectious agent
  • Reservoir’s
  • Portal of exit
  • Means of transmission
  • Portal of entry
  • Susceptible host
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2
Q

What is meant by the word ‘virulence’?

A
  • The ability of a microbe to cause disease
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3
Q

In relation to the infectious agent, What is meant by the word ‘dose’?

A
  • The number of microbes entering the body
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4
Q

Virulence factors include exotoxins and endotoxins. What are 2 examples of exotoxins?

A
  • P. gingivalis (protease)

- S. aureus (enterotoxin & Leukocidin)

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5
Q

Virulence factors include exotoxins and endotoxins. What is an example if an endotoxin?

A
  • Lipopolysaccharides (P. gingivalis & E. coli)
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6
Q

What is the infectious dose of an infectious agent usually expressed as?

A
  • Usually expressed as infectious dose 50 (ID50 - the dose you can get a 50% effect in the test species)
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7
Q

What is the infectious dose of TB?

A
  • 1 bacillus
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8
Q

What is the infectious dose of Syphilis?

A
  • 57 bacteria (ID50)
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9
Q

What is the infectious dose of E. coli 0157?

A

<10 cfu

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10
Q

What is the infectious dose of the influenza virus?

A

<10 (tissue culture ID50)

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11
Q

Microbes are ubiquitous in nature. What does this mean?

A
  • They are found everywhere
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12
Q

Where do most pathogenic microbes that infect humans come from?

A
  • Other humans
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13
Q

Most pathogenic microbes that infect humans come from other humans, but where else can they come from? (3 points)

A
  • Animals: Some human pathogens come from animals (zoonoses) e.g. anthrax
  • Environment: Some human pathogens originate from the environment e.g. Clostridium tetani spores in soil
  • Fomites: contaminated objects or surfaces
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14
Q

What is Zoonoses?

A
  • A disease that can be transmitted to humans from animals
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15
Q

Sometimes microbes can be transmitted to humans by fomites (contaminated objects or surfaces). What 2 categories can this be divided into?

A
  • Medical equipment surfaces

- House keeping surfaces

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16
Q

What does prodrome mean?

A

An early symptom indicating the onset of a disease

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17
Q

What is an incubation period?

A
  • The time between contamination and the development of symptoms
  • Varies widely for different infections
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18
Q

What do longer incubation periods of diseases permit? (2 points)

A
  • Longer time periods when the infecting microbe may spread to others
  • Greater spread of disease because of more human contact
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19
Q

What is an example of a disease that has asymptomatic carriers?

A
  • Carriage of blood-borne viruses, e.g. HIV
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20
Q

What Is meant by colonisation?

A

The presence of micro-organism(S) in or on a host, with the growth and multiplication, but without any overt clinical expression (infection) at the time the micro-organism is isolated

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21
Q

What is an endogenous reservoir?

A
  • From body’s own flora
22
Q

What is an asymptomatic carrier of a disease?

A
  • An infected person with no clinical evidence of disease, though signs and symptoms of the disease may have been evident earlier
  • Carriers as well as their contacts are usually not aware of their infectious state
23
Q

What is an exogenous reservoir?

A
  • From external flora that is usually acquired by transmission of infection
  • Diseases caused by microbes from external sources e.g. influenza
24
Q

When can an endogenous reservoir be infectious? (2 points)

A
  • If flora become ecologically harmful due to population/gene expression shifts e.g. periodontal disease and dental caries
  • If they become displaced to another body site or are allowed to invade deeper tissues e.g. post surgical infections
25
Q

Microbes must escape from the source to colonise a new host. Mechanisms of escape vary depending upon the source. What are the 2 ways the mode of escape can be?

A
  • Natural (e.g. coughing or sneezing)

- Artificial (e.g. blood donation or dental handpiece aerosols)

26
Q

Give a few examples of hoe microbes can escape from the body? (13 possible points)

A
  • Tears
  • Nasal secretions
  • Saliva
  • Blood in saliva
  • Respiratory fluids and sputum
  • Blood and tissue fluids exiting through small breaks in the skin or through injuries
  • Contact with the skin
  • Breast milk
  • Faeces
  • Intestinal fluids
  • Semen
  • Vaginal secretions
  • Urine
27
Q

COSHH classifies human pathogens into 4 hazard groups based on what 4 things?

A
  • The ability to cause infection
  • The severity of the disease that may result
  • The vaccine and treatment available
  • The risk of population spread
28
Q

What is meant by ‘R0’ (R naught)?

A
  • The number of cases one case generates on average over the course of its infectious period
29
Q

When R0 (R naught) <1, What does this mean?

A
  • The infection will dies out in the long run
30
Q

When R0 (R naught) >1, What does this mean?

A

The infection will be able to spread in a population

31
Q

What are the factors that can affect R0 (R naught)? (3 points)

A
  • Duration if infectivity
  • Infectiousness
  • Number of susceptible people
32
Q

How many types of (influenza) RNA viruses have segmented genomes?

A
  • Three types: A, B & C
33
Q

What kind of outbreak can occur with Type A and B influenzas and what are the 2 surface proteins?

A
  • Major outbreaks

2 surface proteins:

  • Haemaglutinin H1-15
  • Neuraminidase N1-9
34
Q

What is pathophysiology?

A
  • The disordered physiological processes associated with disease or injury
35
Q

What does infection of the upper respiratory tract and the lower respiratory tract cells equal?

A

Respiratory tract symptoms

36
Q

What are common symptoms of a mild (uncomplicated) form of influenza? (4 points)

A
  • Fever
  • Cough
  • Headaches
  • Fatigue
37
Q

What are common symptoms of a severe (complicated) form of influenza? (3 points)

A
  • Bacterial pneumonia
  • Ear & sinus infections
  • Worsening of chronic medical conditions (asthma, heart disease)
38
Q

What is the incubation period for influenza?

A
  • 2-3 days
39
Q

When is someone with the influenza virus infectious?

A
  • Once symptoms appear
40
Q

Where does the influenza virus shed from?

A

Shed in upper respiratory tract secretions

41
Q

Once a person is infectious with influenza, how long a re they infectious for?

A
  • 3-5 days

- Children are infected for longer

42
Q

How long can influenza A & B survive on steel and plastic?

A

24-48 hours

43
Q

Hoe long can influenza A & B survive on cloth, paper and tissues?

A
  • For <8-12 hours
44
Q

For how long can transmission of a virus occur from steel to hands?

A

Over 24 hours

45
Q

For how long can transmission of a virus occur from paper tissue to hands?

A

For 15 minutes

46
Q

How long will a virus survive on hands for transmission?

A
  • Approx 5 mins
47
Q

What are 4 ways that viruses can enter the body?

A
  • Respiration (aerosols)
  • Inhalation (all particles)
  • Direct contact (droplets )
  • Indirect contact (settled particles - face touching)
48
Q

What are 4 examples of patients that are at particularly high risk of complicated infections of influenza?

A
  • Elderly
  • Young children
  • Pregnancy
  • Chronic medical conditions (diabetes, asthma, heart disease)
49
Q

How much more likely are patients with health conditions likely to die from the flu?

A
  • 18x more likely
50
Q

The flu vaccination is offered to children as kids are more infectious for longer periods of time and tent to act as a reservoir. What children is the vaccine offered to and what is the vaccine?

A
  • Children aged 2-5
  • Primary school aged children
  • Nasal spray (live attenuated virus)

BDS2 BAMS (57 decks)

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