Session 7 - Preventing Infections

Question 1

what is person to person indirect transmission

Answer 1

where a vector is required to transfer a disease between patients

Question 2

what is an endemic disease

Answer 2

the rate of a disease that you would normally expect to see in a population for a specific organism

Question 3

what is an outbreak

Answer 3

where there are 2 or more linked cases in a time and place

Question 4

what is an epidemic

Answer 4

where the rate of infection is greater than the usual background rate

Question 5

what is a pandemic

Answer 5

a world wide epidemic - a very high rate of infection across many countries

Question 6

what is antigenic drift

Answer 6

when the influenza virus combines 2 or more different strains giving a mixture of antigens on its surface. Therefore more people are susceptible

Question 7

what is antigenic shift

Answer 7

where mutation causes a new strain of a virus to be produced as a new antigen is produced meaning theres a loss of immunity as everyone is susceptible

Question 8

what is the basic reproduction number

Answer 8

the average number of cases on case generates over the course of its infectious period in an otherwise uninfected population

Question 9

what does it mean if R0>1

Answer 9

there is an increase in cases

Question 10

what does it mean if R0=1

Answer 10

there is a stable number of cases

Question 11

what does it mean if R0<1

Answer 11

there is a decrease in cases

Question 12

what changes in a pathogen result in outbreaks of infection

Answer 12

new antigens (antigenic shift/drift), changes in virulence factors or antibacterial resistance

Question 13

what changes in hosts result in outbreaks of infection

Answer 13

if the host is immunocompromised e.g. undergoing cancer treatment or HIV

Question 14

what factor determines transmissibility

Answer 14

the infectious dose of a pathogen - different infections require different numbers of microbes in order to cause the infection

Question 15

what is the shape of an endemic curve

Answer 15

bell shaped

Question 16

what is the nature of a small scale outbreak

Answer 16

stochastic/ random

Question 17

what interventions can be made on the 4 P’s to prevent infection

Answer 17

Pathogen - reduce vector/pathogen
Patient - improve health and immunity
Practice - protective equipment and behavioural changes
Place - environmental changes

Question 18

how can you reduce/eradicate a pathogen

Answer 18

• antibacterial
• sterilisation
• decontamination

Question 19

how can you reduce/eradicate vectors

Answer 19

eliminate the breeding sites

Question 20

how can you improve a patients health and immunity

Answer 20

Health - nutrition and medical treatment

Immunity - passive though maternal antibodies and IV immunoglobin and active though vaccinations

Question 21

what is herd immunity

Answer 21

vaccinating the majority of a population giving indirect protection to those who aren’t vaccinated as well as direct protection

Question 22

what does the vaccination number for herd immunity depend on

Answer 22

the reproduction number for that infection

Question 23

what environmental changes can be done to prevent infection

Answer 23

• safe water and air
• good quality housing
• healthcare facilities

Question 24

what are the advantages of preventing infection

Answer 24

• decreased incidence

- elimination of disease/organism

Question 25

what are the disadvantages of preventing infection

Answer 25

• decreased exposure to a pathogen gives decreased immune stimulus leading to decreased antibody production and so people are more susceptible therefore an outbreak is more likely
• there are later average ages of exposure making the severity of the infection worse