Session 8 - Infection prevention

Question 1

Give three different mechanisms of infection

Answer 1

• Common source
  
  • Person-to-person direct
  • Person-to-person indirect

Question 2

Give three examples of common sources and the infections associated

Answer 2

• Food/water - Food poisoning organisms
  
  • Environmental - Legionella Pneumophilia
  • Animals - Rabies

Question 3

Give three examples of person to person direct infection

Answer 3

• Influenza
  
  • Norovirus
  • Neisseria Gonnorhoeae

Question 4

Give three examples of person to person indirect transmission (involved a vector)

Answer 4

• Mosquitos - Malaria, dengue
  
  • Cats - Toxoplasmosis
  • Ticks - Lyme disease, spotted fever

Question 5

What is an endemic disease?

Answer 5

• The usual background rate

Question 6

What is an outbreak?

Answer 6

• Two or more cases linked in time and place

Question 7

What is an epidemic?

Answer 7

A rate of infection greater than the usual background rate

Question 8

What is a pandemic?

Answer 8

Very high rate of infection spreading across many regions, countries and continents

Question 9

What is a basic reproduction number?

Answer 9

The average number of cases one case generates over the course of its infectious period, in an otheriwse uninfected, non-immune population

Question 10

What if Ro>1?

Answer 10

Increase in cases

Question 11

If Ro=1?

Answer 11

• Stable number of cases

Question 12

What if Ro <1?

Answer 12

• Decrease in cases

Question 13

Give three reasons for outbreaks

Answer 13

• New pathogen
  
  • New hosts (compromised immunity, healthcare effects)

New practice

Question 14

What is an infectious dose?

Answer 14

Number of micro-organims required to cause infection

Question 15

Give an organism with a high infectious dose

Answer 15

• Salmonella - Requires >10^5 organisms

Question 16

Give an organism with a low infectious dose

Answer 16

• Escherichia coli - Very low <10 organisms

Question 17

Give three factors which vary the necessary infectious dose

Answer 17

• Micro-organism
  
  • Presentation of micro-organism
  • Immunity of potential host

Question 18

What are the four P’s of infection?

Answer 18

• Pathogen
  
  • Patient
  • Practice
  • Place

Question 19

How do you reduce outbreaks due to pathogens?

Answer 19

• Reduce/eradicate pathogen
		○ Antibacterials including disinfectants
		○ Decontamination
		○ Sterilisation
	• Reduce/eradicate vector 
		○ Eliminate vector breeding sites

Question 20

How do you reduce outbreaks due to patients?

Answer 20

• Improved health immunity
		○ Passive 
		○ Active
	• Improved health
		○ Nutrition
		○ Medical treatment

Question 21

What is passive immunity?

Answer 21

Passage of maternal antibodies across placenta

Question 22

Why does the incidence of meningitis increase dramatically at three months after birth

Answer 22

• Newborns have immunity from mothers antibodies up to that point

Question 23

How do you reduce outbreaks due to practice?

Answer 23

• Behavioural change

Question 24

How do you reduce infections due to place?

Answer 24

• Environmental

* Engineering

Question 25

What is herd immunity?

Answer 25

• If 90-95% population vaccinated, gives protection to those who are not as pathogen has no vector

Question 26

Give two categories of changes in practice which will protect infection?

Answer 26

• Avoidance of pathogen or its vector

* Behavioural

Question 27

Give two main methods of avoiding pathogens or vector as a change in practice to prevent infection

Answer 27

• Geographic (Don’t go there!)

* Protective clothing, equipment

Question 28

Give three big behavioural changes which prevent infection

Answer 28

• Safe sex
  
  • Safe disposal of sharps
  • Food and drink preparation

Question 29

Give an example of how place can be modified to prevent infection

Answer 29

• Safe water
  
  • Safe air
  • Good quality housing
  • Well designed healthcare facilities

Question 30

What are the good consequences of increased control of bacteria?

Answer 30

• Decreased incidence or elimnation of disease/organism

Question 31

What are the negative consequences of increased contorol of bacteria?

Answer 31

• Decreased exposure to pathogen -> Decreased immune stimulus -> Decreased antibody -> Increased susceptibility -> Outbreak (polio, decreased exposure when young means bad when old)

Later average ages of exposure -> Increased severity

Question 32

What is congenital rubella virus?

Answer 32

If infected in first 12-14 weeks of pregnancy will suffer from abnormal development