Infection Prevention

Question 1

Describe the communicable nature of infections

Answer 1

The communicable nature of infections 
• Many infections are transmissible
– From a non-human source to humans 
– From person to person
• Directly 
• Indirectly

Question 2

Give examples of sources of common sources of infection

Answer 2

Environmental - Legionella pneumophila
Food/water - food poisoning organisms – onward transmission possible like from person to person e.g. with salmonella
Animals - rabies – onward transmission possible

Question 3

Give an example of person to person indirect transmission

Answer 3

Vectors can transmit infection from person to person. Competent vector = can transfer it. e.g. Mosquitos - malaria

Question 4

Give example to person to person diets transmission

Answer 4

Influenza
Norovirus
Neisseria gonorrhoea
Exponential increase as each person can infect multiple people

Question 5

What is endemic disease

Answer 5

The usual background rate - normally expect to see in a normal population

Question 6

Define outbreak

Answer 6

Two or more cases linked in time or place

Question 7

Define epidemic

Answer 7

A rate of infection greater tan the usual background rate

Question 8

Define pandemic

Answer 8

Very high rate of infection spreading across many regions, countries, continents - e.g. if people dont have antibodies for a particular pathogen

Question 9

What is basic reproduction number?

Answer 9

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

• If Ro >1 -> increase in cases
• If Ro =1 -> stable number of
cases
• If Ro <1 -> decrease in cases

As people die or recover - number of susceptible people decreases so secondary cases decrease

Question 10

How does a new pathogen case outbreaks/epidemics/pandemics

Answer 10

May be a new strain of virus, may be novel in virulence factors or it may be more rsistat to antibiotics - ability to treat patients would decrease e.g. with MRSA

Question 11

How does new hosts cause outbreaks/epidemics/pandemics

Answer 11

Some ppl not immune - have babies - increase of ppl not immune - if pathogen introduces there are large umber of people who are susceptible.e.g. With chicken pox outbreaks
May create new patients through healthcare - leads to outbreaks

Question 12

How does new practice cause outbreaks/epidemics/pandemics

Answer 12

E.g. tattoo w/ low standards of hygiene - blood borne viruses
Importing meat from other countries when animal handling standards are low
Ppl who get E. coli - usually elderly - as more people get elderly higher proportion of people with E. coli

Question 13

What are factors determine transmissibility?

Answer 13

Infectious dose –
– number of micro-
organisms required to cause infection
– Varies by:
• micro-organism 
• presentation of micro-organism 
• immunity of potential host

Question 14

What is an epidemic curve

Answer 14

Shows the number of people infected at each time interval against time. Start of with susceptible population, get infected, either recover or die. Eventual the organism peters out - got rid of completely or resistance

Question 15

How do changes in weather lead to outbreaks

Answer 15

Some organisms susceptible to weather conditions - warm weather - transmission died down when theres ar currents like air con . Winter months - people gathered together - more likely to transmit

Question 16

What is stochasticity of small scale outbreaks

Answer 16

having a random probability distribution or pattern that may be analysed statistically but may not be predicted precisely.
Not all of them follor the curve

Question 17

Describe intervention at a pathogen/vector level

Answer 17

• Reduce/eradicate pathogen
– Antibacterials including disinfectants e.g. disinfectant wipes, hand gel
– Decontamination
– Sterilisation

• Reduce/eradicate vector
– Eliminate vector breeding sites e.g. draining marshland where mosquitos lay eggs

Question 18

Describe interventions at the patient level

Answer 18

• Improved health
– nutrition
– medical treatment

• Immunity
– Passive e.g. maternal antibody, intravenous immunoglobulin
– Active i.e. vaccination - e.g. smallpox vaccination - identifying people with smallpox - setting up a ring of vacination around them to preventt transmission outside a particular area

Question 19

What is herd immunity

Answer 19

It arises when a high percentage of the population is protected through vaccination against a virus or bacteria, making it difficult for a disease to spread because there are so few susceptible people left to infect.

This can effectively stop the spread of disease in the community. It is particularly crucial for protecting people who cannot be vaccinated. These include children who are too young to be vaccinated, people with immune system problems, and those who are too ill to receive vaccines (such as some cancer patients).

The proportion of the population which must be immunised in order to achieve herd immunity varies for each disease but the underlying idea is simple: once enough people are protected, they help to protect vulnerable members of their communities by reducing the spread of the disease.

Question 20

Describe intervention through practice

Answer 20

• Avoidance of pathogen or its vector
– Geographic, “Don’t go there”
– Protective clothing, equipment
• long sleeves, trousers against mosquito bites
• Personal protective equipment in hospitals
– gowns, gloves, masks

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

Question 21

Describe intervention in terms of place

Answer 21

• Environmental engineering
– Safe water e.g. separating sewage from drinking water 
– Safe air 
– Good quality housing 
– Well designed healthcare facilities

Question 22

What are good consequences of control

Answer 22

GOOD
• Decreased incidence or elimination of disease/organism
– Smallpox completely eradicated
– Polio - very few
– Dracunculiasis - a worm infection almost eradicated (ppl put their feet in water - eggs go in water - make sure drinking water filtered/not contaminated)

Question 23

What are bad conseqeucnes of control

Answer 23

• Decreased exposure to
pathogen -> decreased immune stimulus -> decreased antibody -> increased
susceptibles -> outbreak
• Later average age of exposure
-> increased severity
– e.g. polio, hepatitis A, chicken pox, congenital rubella syndrome

Question 24

What is surveillance

Answer 24

Server lance of what is happening now, here elsewhere? And what might happen?
Centres for disease control have programs where they actively search for new diseases emerging