Infection - Preventing Infections

Question 1

Give some examples of common sources that can infect more than one person

Answer 1

• food/water
• animals
• other environmental sources eg. plumbing systems can transmit Legionnaire’s

Question 2

Give some examples of infections that are transmitted from person to person

Answer 2

Influenza, norovirus, neisseria gonorrhoea (many more)

Question 3

How is malaria transmitted?

Answer 3

Person to mosquito to person, so through a vector

Question 4

What is endemic disease?

Answer 4

The usual background rate of disease found in the environment

Question 5

What is an ‘outbreak’ of disease?

Answer 5

Two or more cases linked in time and place

Question 6

What is an ‘epidemic’ of a disease?

Answer 6

A rate of infection greater than the usual background rate

Question 7

What is a ‘pandemic’ of an infection?

Answer 7

Very high rate of infection spreading across many regions, countries and continents. This becomes possible in cases of a virus undergoing antigenic shift

Question 8

What is the basic reproduction number (R0)?

Answer 8

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

Question 9

What does it mean if a disease has an R0 of 1?

Answer 9

There will be a stable number of cases

Question 10

What does it mean if a disease has an R0 of more than 1?

Answer 10

There will be an increase in cases, eg. Measles has 12-18 so it will cause lots of cases

Question 11

What does it mean if a disease has an R0 of less than one?

Answer 11

There will be a decrease in the number of cases

Question 12

Give some reasons for outbreaks of disease

Answer 12

• new pathogen (new antigens, virulence factors or antibacterial resistance)
• new hosts
• new practice (social, healthcare)

Question 13

What is the ‘infectious dose’?

Answer 13

The number of microorganisms required to cause infection. It varies by microorganism, presentation of microorganism and immunity of potential host.

Question 14

Why is it possible to consume water contaminated with cholera but not get cholera?

Answer 14

A relatively large amount of cholera organisms is required to cause infection

Question 15

What is an epidemic curve?

Answer 15

A bell-shaped curve which illustrates how the number of people infected changes over time - at first not many are infected, then lots are, then not many as most people have already been infected

Question 16

What interventions can be made at the pathogenic level to prevent infection?

Answer 16

• reduce/eradicate pathogen using antibacterials, decontamination and sterilisation
• reduce/eradicate vector by eliminating breeding sites

Question 17

What interventions can be made at a patient level to prevent infection?

Answer 17

• improved nutrition and medical treatment
• improved passive immunity (maternal antibody, IV immunoglobulin)
• improved active immunity (vaccination)

Question 18

What is herd immunity?

Answer 18

A form of indirect protection from infectious disease that occurs when a large percentage of a population has become immune to an infection, thereby providing a measure of protection for individuals who are not immune

Question 19

What interventions can be made in the environment to prevent infection?

Answer 19

Environmental engineering can help to provide:

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

Question 20

What practices can be adopted by healthcare professionals and the wider population to prevent spread of infection?

Answer 20

• avoid geographical area of pathogen/vector
• use protective clothing/equipment, eg. wearing long sleeves and trousers to protect against mosquito bites, or using gowns/gloves/marks in hospitals
• behavioural modifications, eg. practicing safe sex, safe disposal of sharps and food/drink preparation

Question 21

Give some good consequences of control of infection

Answer 21

Decreased incidence/elimination of disease/organism, as in the cases of smallpox, polio and dracunculiasis

Question 22

Give some bad consequences of infection control

Answer 22

• decreased exposure to pathogen can result in decreased immune stimulates and therefore less antibodies. This means there will be more susceptible individuals and there is a risk of outbreak occurring
• later average age of exposure leads to increased severity of illness