Infection Prevention

Question 1

What is an example of a pathogen that can be transmitted environmentally but not from person to person?

Answer 1

Legionella pneumophila

Question 2

What is an example of an infection that is transmitted from animal to person?

Answer 2

Rabies

Question 3

What are some examples of pathogens that are transmitted from person to person directly?

Answer 3

Influenza, Norovirus, Neisseria gonorrhoea

Question 4

What is an example of an infection that is transmitted from person to person indirectly?

Answer 4

Malaria (use of mosquitos)

Question 5

What is meant by endemic disease?

Answer 5

Usual background rate

Question 6

What is meant by an outbreak?

Answer 6

Two or more cases linked in time and place

Has to be some plausible connection between two cases

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, continents

Question 9

What is antigenic shift?

Answer 9

Antigenic shift is the process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains.

Question 10

What is antigenic drift?

Answer 10

Antigenic drift is a mechanism for variation in viruses that involves the accumulation of mutations within the genes that code for antibody-binding sites.

Question 11

What is R0?

Answer 11

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

Question 12

What happens to the number of cases if R0 > 1?

Answer 12

Increase in cases

Question 13

What happens to the number of cases if R0 = 1?

Answer 13

Stable number of cases

Question 14

What happens to the number of cases if R0 < 1?

Answer 14

Decrease in cases

Question 15

What is the infectious dose?

Answer 15

Number of micro-organisms required to cause infection

Question 16

What interventions can be made in the transmission of infections?

Answer 16

Reduce/eradicate pathogen - antibacterials, decontamination, sterilisation

Reduce vector (mosquito spray, eliminate vector breeding sites)

Improved health of patient, nutrition, immunity

Question 17

What is herd immunity?

Answer 17

The resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination.
“the level of vaccination needed to achieve herd immunity varies by disease”

Question 18

How can practices be changed to reduce infection spread?

Answer 18

Avoidance of pathogen (geographically, protective clothing)

Behavioural (safe sex, safe disposal of sharps, safe food and drink preparation)

Question 19

What are the positive consequences of infection control?

Answer 19

Decreased incidence or elimination of disease/organism

Question 20

What are the negative consequences of infection control?

Answer 20

Decreased exposure to pathogen -> decreased immune stimulus -> decreased antibody production -> increased susceptibility -> outbreak

Also, later average age of exposure so increased severity of infection (eg in polio, hep A, chicken pox)