Infection prevention Flashcards
Give an example of an environmental source of infection
Is onward transmission possible?
Where is it found?
- Legionella pneumophila
- Found in contaminated water
- Onward transmission is not possible
Give an example of a food/water source of infection
Is onward transmission possible? (3)
Food poisoning (gastroenteritis) organisms ie listeria monocytogenes, E.coli, salmonella
- Onward transmission is possible
Give an example of an animal source of infection
Is onward transmission possible? (2)
- Rabies
- COVID - 19
- Onward transmission is possible
Name some diseases that (direct) person to person transmission is the predominant mode of transmission (3)
Influenza
Norovirus
Neisseria gonorrhoea
An example of Person to person indirect transmission
Mosquitos (vector) for malaria
What are the consequences of transmission?
What’s endemic disease? What is it dependant on?
The Usual background rate of infection
- Dependant on the time of year
What’s an outbreak?
Two or more cases linked in time and place
What’s an epidemic?
A rate of infection greater than the usual background rate
What’s a pandemic?
Very high rate of infection spreading across many regions, countries and continents
What is R0 (basic reproduction number)?
- Average number of cases one case generates
- over its infectious period
- in an otherwise uninfected non-immune population
What does it mean if R0 >1
Increase in cases
What does R0 = 1 mean
Stable number of cases
What does R0 <1
Decrease in cases
Reasons for outbreaks, epidemics, pandemics
- New pathogen (eg antigens, virulence factors, antibacterial resistance)
- New hosts (eg, non-immunes, healthcare effects)
- New practice (IV drug use/move to new area)
What factors determine transmissibility? (3)
- Infectious dose
(number of microorganisms required to cause infection) - The method of spread - ?airborne/aerosol? Droplets ?direct contact (shingles) ?sexual encounter (i.e. mucous membranes)
- Immunity status of the host ie immunocompromised
What does infectious dose vary with? (3)
- Microorganism type
- Presentation of micro-organism - how are you exposed to it? (aerosol, food, blood borne)
- Immunity of potential host
What does an epidemic curve look like?
Smooth curve up, reaches peak and comes back down
Why is the epidemic curve smooth?
Pattern of transmission:
Susceptible –> infected –> Recovered (with immunity)
What pattern do small scale outbreaks (ie a ward) follow?
Stochastic curve
Irregular and unpredictable
Why can the stochastic nature of small scale outbreaks be misleading?
as people can form conclusions without considering the fact that this may normally occur without any interventions!
Interventions (pathogens) (5)
Interventions (patient) (6)
.
What is herd immunity? (3)
- Large portion of a community (the herd) becomes immune to a disease.
- The spread of disease from person to person becomes unlikely when herd immunity is achieved
- Thus the whole community becomes protected — not just those who are immune.
Why is herd immunity important?
Prevents onward transmission
Practice interventions (10)
Place interventions (4)
Good consequences of control.
Give 3 examples
Decreased insidence/eliminated disease/organism (polio, smallpox dracunliasis)
Bad consequences of control (2)
.
Name some conditions that if you got them at a later age, they would be more severe (4)
- Chicken pox
- Congenital rubella syndrome
- Hepatitis A
- Polio
How can we keep a balance of good and bad consequences?
Surveillance:
- What is happening now, here and elsewhere
AND - What might happen - be aware of risks
