Infection Prevention Flashcards
What does it mean to describe a disease as “communicable”?
This means than many infections are transmissible from:
- A non-human source to humans
- Person to person (either directly or indirectly)
What are some possible sources of infection?
- Environmental - Legionella pneumophilia
- Food / Water - Food poisoning organisms - onwards transmission possible
- Animals - Rabies - onwards transmission possible.
What infections can pass directly from person to person?
- Influenza
- Norovirus
- Neisseria gonorrhoea
What infections can pass indirectly from person to person (via a vector)?
Malaria - via mosquitos
Zika - via mosquitos
Define ‘Endemic Disease’
The usual background rate. - What you expect to see in the population
Define ‘outbreak’
Two or more cases linked in time and place
Define ‘Epidemic’
A rate of infection greater than the usual background rate
Define ‘Pandemic’
Very high rate of infection spreading across many regions, countries and continents. E.g. Swine flu pandemic in 2009
What is R0?
This is the average number of cases one case generates over the course of its infectious period, in an otherwise uninflected, non-immune population.
Measles has a very high R0 because it is airborne so it has a high spread. Pertussis (Whooping cough) also has a high spread because it is spread by airborne droplets.
What are some reasons for outbreaks, epidemics, pandemics?
New pathogen (antigens, virulence factors and antibacterial resistance). - Influenza.
New hosts (non-immunes, healthcare effects) - chickenpox in the winter in nursery / school as new starters or cancer patients which are immune compromised.
New practise (social, healthcare) - tattoos cause Hep B / C, Hep E caused by pigs due to changes in farming practise, E. coli - as proportion of elderly increases, diabetes prevalence increases.
What factors determine tarnsmissability?
- Infectious dose
- Number of micro-organisms required to cause infection
- Varies by:
- Microroganism
- Presentation of micro-organism
- immunity of potential host.
Why does an epidemic curve look like a normal distribution curve?
Firstly, susceptible so lots infected so number of cases increases.
Then either die or recover with antibodies (resistance) so cases drop again.
Cycle then repeated.
What is stochastisity?
This is the ‘random nature’ of small studies.
This is important because it shows that it is difficult to show that intervention has effect as the course of virus is random no matter what happens.
How can you intervene to prevent infection?
Pathogen (and vector) -Reduction or eradication
Patient - improved health immunity
Practise - behavioural change, protective equipment
Place - Environmental engineering
How can you intervene at the pathogen level to remove infections?
Reduce / eradicate pathogen
- Antibacterials including disinfectants
- Decontamination
- Sterilisation
Reduce / eradicate vector
- Eliminate vector breeding sites
