Lecture 3- Communicable disease control Flashcards

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1
Q

Main ways in which people and animals catch and spread disease?

A
  • droplet spread
  • faecal-oral
  • direct contact
  • vector borne
  • blood borne
  • fomites
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2
Q

Droplet spread

A

Covid 19, flu, measles, meningococcal infection

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3
Q

Faecal-oral

A

Typhoid, E.coli, hepatitis A

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4
Q

Direct contact

A

Scabies, impetigo, HSV, STis

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5
Q

Vector borne

A

Malaria, dengue, lyme disease, leptospirosis, rabies

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6
Q

Blood borne

A

HIV, hepatitis B and C

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7
Q

Fomites

A

Non-living object that transmits disease causing pathogens e.g. door handle

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8
Q

The epidemiological triangle

A
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9
Q

Chain of infection

A
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10
Q

example of chain of infection

A
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11
Q
A
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12
Q

Source-Pathway-Receptor

A

Remove any one or block the route… interrupt transmission.

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13
Q

Measures to prevent further cases

  • Kill or inactivate the agent or the source
A
  • Antibiotics
  • Decontamination
  • Disinfection
  • Sterilisation
  • Heat treatment
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14
Q

Measures to prevent further cases

  • Interrupt the pathway of transmission
A
  • Isolation
  • Environmental hygiene
  • Personal hygiene
  • Personal protective equipment (PPE)
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15
Q

Measures to prevent further cases

  • Protect the host i.e. the receptor
A
  • Isolation
  • Immunisation
    • Of the vulnerable
    • Of the contacts
    • Cocoon
  • Chemoprophylaxis
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16
Q

For infection transmission to occur you need an…

A
  • Infectious agent (e.g. a virus or bacterium)…
  • A source of infection (an infectious person or contaminated water
  • An environment which enables infection to spread (an available pathway for infection such as shared space or poor sanitation) …..
  • A population with susceptible people in it (e.g. unvaccinated children exposed to measles
17
Q

What happens if you cant control transmission of a disease? An

A

outbreak

18
Q

What is an outbreak?

A
  • Two or more LINKED cases of an infection
    • (Linked in TIME, PLACE or PERSON)
  • An increase in cases of a disease OVER AND ABOVE the normal background rate of that disease
  • Any case of an infection that doesn’t normally occur in a setting and which carries a high risk to public health e.g. Ebola, Anthrax
19
Q

A cluster?

A
  • An observed (real or perceived) aggregation of cases grouped in a single time period or setting and suspected to be above the expected level (CDC)
    • Not necessarily a proven link between cases (yet)
    • On investigation, may not actually even represent a significant rise in cases (play of chance leads to appearance of cluster)
    • Needs investigation as may lead to discovery of an outbreak
  • May need intervention to prevent an outbreak from occurring e.g. in Wuhan
20
Q

epidemic curves

A
  • point source outbreak
  • extended outbreak
  • propagated outbreak
21
Q
A

point source outbreak

e.g. food poisoning at a party - discrete

22
Q
A

Extended outbreak e.g. contaminated water source

23
Q
A

Propagated outbreak e.g. Covid 19

24
Q

R0=

A

basic reproduction number of the virus

How many secondary cases each primary case produces assuming perfect conditions for pathogen e.g. 100% susceptible host

25
Q

An infectious disease has a basic reproduction number (R0) of 8. 25% of the population are immune to the disease.

Which of the following statements describes the effective reproduction number of this disease?

a) 2
b) 4
c) 6
d) 8
e) 32

A

6

26
Q

superspreaders

A
27
Q

Aims of outbreak management

A
  • Minimise number of Primary Cases
  • Minimise number of Secondary Cases
  • Identify and eliminate continuing hazards (sources of infection)
  • Introduce measures to prevent future outbreaks
28
Q

How do you know you have an outbreak in the first place?

A

Surveillance

e.g. Notifiable disease processes

  • for a number of listed infections, if you come across a case you must tell your local infection control team
  • E.g. meningococcal meningitis, ebola (high consequence disease), MMR, polio
29
Q

investigating an outbreak process

A

Sequential

  1. Establish a case definition
  2. Confirm cases are real
  3. Determine background rate- is this really an outbreak
  4. Case Finding
  5. Describe cases in time, place and person
  6. Plot the epidemic curve
  7. Generate a hypothesis
  8. Test your hypothesis
  9. Generate conclusions
30
Q

Case definition examples

A
  • Must be:
    • Precise
    • Accurate
    • Appropriately sensitive and specific
    • Appropriate for the available facilities
  • Should also enable you to characterise probable vs confirmed infection
31
Q

Example of case definition for measles

A
32
Q

Finding your cases (and contacts)

A
  • Describe them in detail:
    • Demographics
    • Symptoms and TIMING
    • Travel/Other exposures including food
    • Immunisations
    • Ethnic/Cultural/Religious Background
  • Plot your epidemic curve
  • Formulate your hypothesis; what patterns have emerged?
  • Test it: Case-control study
33
Q

Case control example

A
34
Q

Once an association has been made…

A

Convene an Outbreak Control Team (outbreak management group, incident management team)

  • Multidisciplinary team who work together to manage outbreaks
35
Q

Statutory/legal frameworks

A
  • Notifiable infections/agents
  • Control of Disease Act
  • Environmental Health Regulations
  • International health regulations
36
Q

When the outbreak is over

A
  • Declare it over (no new cases within x2 incubation period)
  • Debrief
  • bContingency planning