Infection 8 Flashcards
Give examples of common sources of infection
For each give an infection from that source
Food/Water:
Food poisoning (E. coli, salmonella)
Environment (Air, surfaces, soil):
Leigonella pneumophilus
Animals:
Rabies
Give examples of microorganisms transmitted person to person
Influenza
Norovirus
Nesseria gohorrhea
Give examples of microbiota transmitted person to person via a vector
Mosquitos:
Mararia
Cats:
Toxoplasmosis
Ticks:
Lyme disease, spotted fevers
What are the large scale concequences of transmission of infections?
Define each concequence
Endemic disease:
Background level of disease in a area
Outbreaks:
Two or more cases linked in time and place
Epidemic:
Infection rate of greater than usual (background rate)
Pandemic:
Very high rate of infection across many regions, countries and continents
What is an organisms basic reproduction number (Ro)?
Ro = average number of new cases generated over the course of an infectious period in an otherwise unnaffected, non-immune population
- If Ro = 1 number of cases are stable*
- If Ro = >1 or <1 then number of infections increase or decrease*
Give some examples of the Ro of organisms with different methods of transmission
Measles:
Airborne
Ro = 12-18
Diptheria:
Salivary transmission
Ro = 6-7
Smallpox:
Social contact
Ro = 5-7
HIV:
Sexual
Ro = 2-5
What might be the reasons for outbreaks, pandemics or epidemics?
New pathogen introduced (different antigens, virulence factors)
New hosts (non-immunes, new patients presenting to medical facilities)
New practices (E.g. When surgery became common, When air conditioning invented)
What is ‘infectious dose?
Give examples
Infectious dose:
Number of micro-organisms required to cause infection
Varies by:
- Microorganisms*
- Transmission route*
- Immunity of subjects*
Examples:
Salmonella - Large dose (>10^5 organisms)
Shigella/E. coli - Very low dose (10s of organsims)
What is an epidemic curve?
Graph showing cases over time
Takes the form of a bell curve
Reflects initial large scale infection of a susceptible population, a peak in numbers of infected and eventualy resolution (recovery/death)
List interventions aimed at reduction of transmission of a pathogen
Pathogen:
Reduce/eradicate pathogen or vector
Antibacterials and disinfectants
Decontamination
Sterilisation
Patient:
Improved health (nutrition/medication)
Immunity (Vaccines)
Practice:
Geographic avoidance (E.g. endemic countries)
Protective clothing (PPE, covering skin to avoid mosquito bites)
Behaviours (Safe sex, sharps disposal, food and drink prep)
Place:
Environment engineering
- Separation of sewage and drinking water*
- Good quality housing*
- Well designed healthcare facilities*
Explain the concept of herd immunity
Even if one non-immune person becomes infected in an otherwise largely immune population the pathogen is unlikely to spread significantly due to the very low availability of non-immune hosts
What are the good concequences of infection control?
Decrease of incidence
Elimination entirely (E.g. Smallpox)
What are the bad concequences of infection control?
Decreased exposure to pathogen can lead to increases susceptibility of a population, this can result in an outbreak in a previously resistant/immune population
Later the average age of exposure in many organisms, the more severe the symptoms:
- Polio*
- Hep A*
- Chicken pox*
- Congenital rubella syndrome*
What are the 3 main reasons for a need for antimicrobial use control?
Antimicrobial use leads to resistance
Resistance is effectively irreversible
Antimicrobial development has stalled
What are the 3 main concequences of antimicrobial resistance?
Treatment failure
Prophylaxis failure
Economic costs of infection increase
