Community acquired infections Flashcards
communicable diseases can be transmitted from….
- non-human source to humans - from person to person (directly or indirectly)
communicable diseases can be transmitted from….
- non-human source to humans - from person to person (directly or indirectly)
Source of disease example
- Environmental- legionella pneumophilia
- Food/ water- food poisoning organisms (onwards transmission possible)
- animlas- e.g. rabies- onwards transmission possible
endemic disease
usual background rate
outbreak
two or more cases linked in time and place
epidemic
a rate of ifnection greater than the usual background rate
pandemic
very high rate of infection spreading across many regions, countries and continents
exampel of persons to person direct transmission
- Influenza (can also get from animal)
- Norovirus
- Neisseria gonorrhoea
Person- to person indirect transmission
e.g. mosquito- malaria
Basic reproduction number R0
the average number of cases one case generates over the course of its infectious period, in an otherwise uninfected, non-immune population
if R0 is >1
increase in cases
R0=
stable number of cases
R0<1
decrease in cases
reasons for outbreaks, epidemic, pandemics
1) New pathogens
2) New hosts
3) New practice
New pathogens
- New antigens
- New virulence factors
- New antibacterial resistance
New host
- Non-immunes
- E.g. outbreak of chickenpox in children (immune naïve)
- Healthcare effects
new practice (social, healthcare)
e. g. feeding cows cows- BSE
e. g. popularity of tatoos increase
infectious dose is a factor which determines
which determines a disease transmissibility
what is infectious dose
Number of micro-organisms required to cause infection
infectious dose varies by
- micro-organism
- presentation of micro-organism
- immunity of potential host
stochastic natures of small scale outbreak
Stochastic- represents the element of luck
interventions related to the pathogen
- Reduce/eradicate pathogen (only ever been properly achieved with smallpox)
- Antibacterial including disinfectants
- Decontamination
- Sterilisation
- Reduce/eradicate vectorEliminate vector breeding sites
- E.g. eliminating malaria breeding sites
interventions related to patient
- Improve health
- Nutrition
- Housing
- Medical treatment
- Immunity
- Passive e.g. maternal antibody, intravenous immunoglobulin
- Active i.e. vaccination
interventions related to practice
- Avoidance of pathogen or its vector
- Geographic- don’t go there
- Protective clothing and equipment
- Long sleeves, trousers against mosquito
- Personal protective equipment in hospital (gowns, gloves masks)
- Behaviour
- Safe sex
- Sade disposal of sharps
- Food and drink preparation
interventions related to places
Environmental engineering
- Safe water and air
- Good quality of housing
- Well designed healthcare facilities
Vaccination and heard immunity
How vaccinating a proportion of the population can prevent transmission of a disease, including those not vaccinated
Consequences of control over infectious disease: good
Decreased incidence or elimination of disease/organisms
- Smallpox
- Polio
- Dracunculiasis (worm infection)
Consequences of control over infectious disease: bad
- Decreased exposure to pathogen à decreased immune stimulus –> decreased antibody à increased susceptible à outbreak
- Later average age of exposureà increased severity
- E.g. polio
- Hepatitis A
- Chicken pox
- Congenital rubella syndrome
