Control of communicable diseases H&S Flashcards
What is the chain of infection?
- A microorganism
- A reservoir
- Path from reservoir
- Mode of transmission
- Path of entry
- Susceptible hosts
What are reservoirs and give examples of species which can harbour communicable diseases?
- Reservoirs: places where infectious agents live and reproduce.
- Examples: humans, animals (bats, domesticated animals e.g swine flu), environment (water, air, soil e.g vibrio cholerae)
Explain the path from reservoir/mode of transmission/path of entry of communicable diseases
- Direct transmission
1. Faeco-oral route (hands to mouth / often via food)
2. Direct contact (skin-to-skin or mucous membrane to mucous membrane. STIs, scabies) - Indirect:
1. Vector-borne: Transmitted by a non-human LIVING organism. E.g malaria
2. Vehicle-borne: Transmitted by a non-human, NON-LIVING object. E.g hypodermic needles or surgical equipment –> HIV and Hep B - Airborne: Transmitted through air, droplets or aerosols released into the air by infected host breathed in by someone else, through respiratory tract or mucus membranes. E.g Sars-Cov2, TB, legionells
What can cause a host to be susceptible to an infectious agent?
- Immunity
- Immunosuppression: extremes of age, illness, medical treatment
- Genetics: can reduce or increase risk
- Lifestyle factors: alcoholism increases risk, nutrition status
Factors that affect transmission of communicable disease
- Population density (>PD = rapid transmission)
- Sanitation (poor sanitation = significant faecal-oral outbreak)
- Vaccination coverage (herd immunity)
- Deprivation/poverty (less able to take preventative action & increased chance of becoming exposed to an infection. Also, underlying health conditions increase susceptibility to infection and risk of poor outcome. Also, less able to afford healthcare services)
- Access to healthcare
- Travel
Define an outbreak of infectious disease
2 or more people experiencing a similar illness are linked in time or place
A greater that expected rate of infection compared with the usual background rate for the place and time where the outbreak has occurred
How can each part of the chain of infection be targeted to prevent outbreaks?
- Infectious agent: treatment of infected patient
- Reservoir: culling of birds
- Path of exit: cough etiquette
- Mode of transmission: decontamination and disinfection
- Path of entry: shielding
- Susceptible host: immunisation
Different types of surveillance of communicable diseases
- Passive surveillance: routinely collected data
- Active surveillance: specifically collected data, usually reserved for more contagious diseases
- Sentinel surveillance: provides a rough estimate of disease incidence. Uses a sample of reporting units e.g GP practices
- Enhanced surveillance: A form of active surveillance. Usually limited to a particular time/place/purpose e.g monitoring vaccine effectiveness
Different types of information that surveillance of communicable diseases can provide
- Incidence of disease
- Geographical distribution
- Seasonal distribution
- Age and sex distribution
- Early warning signals and help detect outbreaks
Different hospital acquired infections
- C.diff
- MRSA
- CPE
- Legionella pneumophilia
- Norovirus
- BBV
- Hospital acquired pneumonia
- Catheter associated UTI
- Surgical site infections
How to prevent hospital acquired infections
- Education
- Screening
- Isolation/cohorting
- Disinfection & decontamination
- Environmental cleaning
- Learning from previous events
- Hand hygiene
- Good communication
How can we target the chain of infection to manage hospital acquired infections?
- Micro-organism: eradication
- Reservoir: cleaning, isolation
- Path of exit: PPE
- Mode of transmission: PPE, hand hygiene
- Path of entry: hand hygiene
- Susceptible host: skin care
