S5 Infection Prevention

Question 1

What are some examples of sources for e.g. Legionella pneumophilia, food poisoning organisms, rabies?

Answer 1

Legionella - environmental
Food poisoning - food/water
Rabies - animals

Question 2

How can infections be spread?

Answer 2

1. From a common source (then person to person)
2. Person to person (direct)
3. Person to person (indirect - via a vector)

Question 3

What are 3 examples of direct person to person spread?

Answer 3

• influenza
• norovirus
• Neisseria gonnorrhoea

Question 4

What is an example of indirect person to person spread?

Answer 4

Mosquitos spreading malaria (person to person)

Question 5

What is an endemic disease?

Answer 5

The usual background rate of cases

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 that’s greater than the usual background rate

Question 8

What is a pandemic? What sort of pathogen causes this?

Answer 8

A very high rate of infection spreading across many regions/countries/continents

A novel one - one no one is initially immune to

Question 9

What is R0?

Answer 9

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

Question 10

What does it mean if R0 is more than 1?

Answer 10

There is an increase in cases

Question 11

What does it mean if R0 is equal to 1?

Answer 11

There is a stable number of cases

Question 12

What does it mean if R0 is less than one?

Answer 12

There is a decrease in cases

Question 13

What are the reasons for outbreaks, epidemics and pandemics?

Answer 13

• new pathogens - antigens, virulence factors, antibacterial resistance
• new hosts - non-immunes, healthcare effects
• new practice - social, healthcare

Question 14

What factor determine transmissibility of a pathogen? How does this vary?

Answer 14

The infectious dose - the number of microorganisms needed to cause an infection

Varies by microorganism, presentation of microorganism and immunity of potential host

Question 15

What does an epidemic curve shape look like (number of people infected at each time interval vs time)? What are the 3 stages?

Answer 15

A bell-shaped curve

Susceptible, infected, recovered

Question 16

How can a small scale outbreaks curve be defined?

Answer 16

Stochastic - random distribution/pattern (can be analysed with stats but may not be predicted precisely)

Question 17

Where in the infection model can interventions be applied?

Answer 17

• pathogen causing infection with patient
• patient causing infection with pathogen
• pathogen and patient but without infection

Question 18

What interventions can be applied to the pathogen/vector?

Answer 18

Reduction or eradication

• antibacterials (incl. disinfectants)
• decontamination
• sterilisation
• eliminate vector breeding sites

Question 19

What interventions can be applied to the patient?

Answer 19

Improved health

• nutrition
• medical treatment

Immunity

• passive - maternal antibodies, intravenous immunoglobin
• active - vaccination

Question 20

What interventions can be applied to the practice?

Answer 20

• behavioural - are sex, safe disposal of sharps, food/drink prep
• change
• protective equipment - clothing and equipment (long sleeves, PPE)
• geographic - avoid area where pathogen is prominent

Question 21

What interventions can be applied to the place?

Answer 21

Environmental engineering

• safe water
• safe air
• good quality housing
• well designed healthcare facilities

Question 22

What are the good consequences of controlling an infection?

Answer 22

Decrease incidence/elimination of a disease/organism e.g. small pox, polio, dracunculiasis

Question 23

What are the bad consequences of controlling an infection?

Answer 23

• decreased exposure to a pathogen —> deceased immune stimulus —> decreased antibody —> increased susceptibles —> outbreak
• leads to a later average age of exposure when severity is increased e.g. polio, chickenpox, hepatitis A