Infection Prevention

Question 1

Communicable nature of infections

Answer 1

Many infections are transmissible 
	from a non human source to humans 
	from person to person 
		directly 
		indirectly

Common source examples - environmental (legionella pneumonia)
Food/water - food poisoning organisms
Animals - rabies

Person to person examples - influenza, norovirus, neisseria gonorrhoea

Indirect person to person (i.e. through a vector) = mosquitoes - malaria

Question 2

Consequences of transmission

Answer 2

Endemic disease - usually background rate (on average a certain amount of people each year will get norovirus)

Outbreak - 2 or more cases linked in time and place

Epidemic - rate of infection greater than the usual background rate

Pandemic - very high rate of infection spreading across many regions, countries and continents

Question 3

Basic reproduction number

Answer 3

Ro = the average number of cases 1 case generates over the course of its infectious period, in an otherwise uninfected non - immune population

If Ro > 1 this leads to an increase in cases

If Ro = 1 this leads to a stable number of cases

If Ro < 1 the leads to a decrease in cases

Question 4

Reasons for outbreaks, epidemics and pandemics

Answer 4

New pathogen (antigens, virulence factors, antibacterial resistance) - e.g. corona virus

New hosts (non-immunes, healthcare effects) e.g. non immune patient gets sick

New practice (social, healthcare) e.g. anti-vaxers

Factors determining transmissibility:
 Infectious dose - 
	i.e. number of micro-organisms required to cause infection 
Varies by:
	micro-organism 
	presentation of micro-organism
	immunity of potential host

Question 5

Epidemic curves

Answer 5

Patterns can be seen with the neurovirus epidemic curve - usually increases during winter time and is smaller in summer time

However key to remember that small scale outbreaks are stochastic - i.e. the probability of duration, severity and number of cases is random

Question 6

Intervention

Answer 6

Want to try and limit the spread of the disease - so need identify areas where we can intervene to achieve this

Pathogen - reduction or eradication (e.g. using antibiotics)

Patient - improve the overall health of the patient, provide vaccines for immunity for some of these diseases

Practice - behavioural change of patients and doctors to prevent the passing on of pathogens, use protective equipment

Question 7

Interventions at the pathogens and vector level

Answer 7

Reduce/eradicate pathogen

• Antibacterials including disinfectants
• Decontamination
• Sterilisation

Reduce/eradicate vector
- Eliminate vector breeding sites

Question 8

Interventions at the patient level

Answer 8

Improved health
- nutrition - medical treatment

Immunity
- Passive e.g. maternal antibody, intravenous immunoglobulin
- Active i.e. vaccination
E.g. Herd immunity

Question 9

Interventions with regards to practice (and place)

Answer 9

Avoidance of pathogen or its vector

Geog

Question 10

Consequences of control

Answer 10

Good -
Decreased incidence or elimination of disease
e.g. smallpox, polio

Bad -
decreased exposure to pathogen, leads to a decreased immune stimulus, which leads to decreased antibody count which leads to increased susceptibility leading to an outbreak

If our average age of exposure increases then sometimes there is increased severity
e.g. polio, HepA, chicken pox (if you get chicken pox when you are little he affects are much less worse than if you get it later in life)