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Communicable Disease Control MPH > Epidemiology & Surveillance > Flashcards

Epidemiology & Surveillance Flashcards

1
Q

What is an emerging infection?

A

infections that have newly appeared in a population, or have previously existed but are rapidly increasing in incidence or geographic range

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2
Q

Focus of a PH professional for CDC

A
  • Contacts
  • Source
  • Prevention
  • Control
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3
Q

What is an epidemiologic transition

A

phenomenon whereby the prevalence and type of disease experienced by a country evolves with development. Over time (development), prevalence of infectious diseases falls and that of non communicable diseases increases

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4
Q

What country characteristics increase infectious diseases

A
  • low wealth
  • low development
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5
Q

Why are IDs more common in less developed settings (5)

A

lack of safe drinking water
poor sanitation
overcrowded living conditions
limited access to healthcare
malnutrition

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6
Q

What are the negative effects of urbanization (5)

A

Pollution
Accidents
Heat Island effects
Climate change
High population density –> ID outbreaks (particularly in overcrowding and poor WASH)

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7
Q

What is the effect of globalisation & global trade?

A

economic linkages & dependencies between countries –> greater movement of peoples, goods & services.
Global trade –> environmental degredation & climate change

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8
Q

Benefits of globalization to ID

A

growth of communications technology
social networking
research links
spread of healthcare technology
–>enable health knowledge & expertise to be widely disseminated

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9
Q

Effects of technological advances & travel

A

air travel –> rapid ID spread.
Import of diseases from endemic countries to non endemic countries
Health tourism - spread both ways
transport of disease vectors & pathogens
food born diseases

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10
Q

Effect of healthcare advances

A

Invasive medicine - creates means for infection to be introduced - including opportunistic.
Antibiotic resistance - increasing concerns especially with spread due to travel

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11
Q

Effect of climate change

A

increased suitable breeding environments for mosquitos & accelerate their lifecycle –> increasing numbers
–> increase in infectious diseases e.g. Malaria & Dengue
Extend breeding habitat for ticks
Increase in extreme weather events –> further ID outbreaks

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12
Q

International initiatives for ICD control

A

GAVI; WHO Essential Medicines list
etc
International health regulations: notifiable diseases, health rules for trade and travel, measures for disinfecting ships etc, health documents required

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13
Q

What is a PHEIC (public health emergency of international concern)

A

an extraordinary event which is determined to constitute a public health risk to other States through the international spread of disease and potentially require a coordinated international response

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14
Q

Early Warning Systems

A

EnterNet (enteric pathogens)
EARSNet (antimicrobial resistance)
EISN (influenza)
GOARN - WHO global outbreak alert and response network

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15
Q

What is ‘One Health’

A

broader focus looking at people, animals, plants and the shared environment as they all interlink – therefore multisectoral approach to health

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16
Q

What is the purpose of epidemiology

A

to identify risk factors & trends in infection

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17
Q

What to look for in terms of distribution of disease

A

Time
Place (geographical link, setting)
Person (contacts of index case & anything specific about the people getting it)

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18
Q

What do communicable disease interventions target

A

Anything along the lifecycle of disease:
source, pathway, receptors
Reservoir –> agent –> host –> reservoir

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19
Q

What is a vehicle

A

a vector that isn’t a living thing. E.g. needle, surgical equipment

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20
Q

How to describe disease

A

Frequency (how often occuring)
distribution (time, place, person)
Determinants (are there common factors e.g. smoking, social deprivation, occupation)

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21
Q

Describe the chain of infection

A

reservoir –> portal of exit –> agent –> mode of transmission –> portal of entry –> host –> person to person spread –> reservoir

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22
Q

Features of Direct transmission

A

Direct contact with infected material or pathogens
e.g. scabies, viral gastroenteritis
Includes fomites
Can have multiple modes of transmission e.g. respiratory diseases -> airborne and direct by droplets settling onto objects

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23
Q

Indirect transmission

A

Vector borne or vehicle borne

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24
Q

Endemic def

A

Persistent level of disease occurrence

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25
Q

Hyper-endemic

A

persistently high levels of diseases occurrence

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26
Q

Sporadic

A

Irregular pattern of occurance

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27
Q

Epidemic

A

Occurrence in an area in excess of what is expected for a given time period

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28
Q

Pandemic

A

Epidemic widespread over several countries

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29
Q

Outbreak

A

2 or more cases of a disease that are linked
OR
occurrence of a disease (can be just 1 case) that is not expected in an area e.g. Ebola in UK
If cases aren’t linked (and not unexpected disease) its not an outbreak its a cluster

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30
Q

Common source outbreak

A

When a group of persons have been exposed to a common source of an infectious agent or toxin. e.g. at the same restaurant

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31
Q

Point source outbreak

A

When the exposure to an infectious agent or toxin has occurred over a brief period of time

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32
Q

Propagated Outbreak

A

 When an outbreak is gradually spreading from person to person.
Epidemic curve is initially separate waves and then they start to merge together as incubation periods etc. start to overlap

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33
Q

How to describe an epidemic curve

A

describe background level of infection (what level for how long)
Describe increase at what week and to what level
Then describe if there is a decline after that

34
Q

What does the incubation period encompass on natural history of an ID

A

Latent period = point in time where person acquires the infection until the point they become infectious.
AND
Asymptomatic infectious period
Then when symptoms develop incubation period stops

35
Q

Infectious period

A

Includes when asymptomatic but infectious and when symptomatic

36
Q

What happens in disease

A

organ/tissue damage (not the same as symptoms

37
Q

What is the secondary case also

A

a primary contact of the index case

38
Q

What is infectious dose

A

quantity of microorganisms needed to produce infection in the host

39
Q

What is infectivity

A

proportion of exposed persons who become infected
aka attack rate

40
Q

What is pathogenicityk

A

proportion of infected persons that develop the disease

41
Q

What is virulence

A

the proportion of persons who develop the disease who become severely ill or die

42
Q

what is disease incidence

A

number of NEW cases occurring over a given time period in a defined population at risk (that are disease free initially)

43
Q

What is incidence rate

A

the number of new cases of a disease divided by the number of persons at risk for the disease. (in a certain time period)

44
Q

What is disease prevalence

A

Number of EXISTING cases at a given point in time in a defined population
Point prevalence (point in time) vs Period prevalence (over a time period).
If prevalence is dropping its because people are dying

45
Q

What are attack rates

A

This measures the proportion of persons in a defined population who experience an acute health event (e.g. infection) during a specified time period (e.g., during an outbreak), i.e. it is a form of ‘cumulative incidence’. It is expressed as a percentage or per 1,000 or 100,000 population.
Often used instead of risk or incidence proportion in short lasting outbreaks
aka infectivity

46
Q

Case fatality rates

A

Proportion of cases who die from it

47
Q

Odds

A

measure of the likelihood of one event occurring compared to another event
odds = number of event A occurring/number of event B occurring
event A normally = cases of disease. event B normally = number of those who don’t get it

48
Q

Odds Ratio

A

Odds ratio: This is ratio of one set of odds against another. Odds ratios are frequently
calculated from case-control studies where we compare the experience of CASES (e.g.
persons with disease) against CONTROLS (persons without disease). For example, if Odds 1 is the number of cases with the exposure divided by the number of cases without the exposure, and Odds 2 is the number of controls with the exposure divided by the number of controls without the exposure. The Odds Ratio is Odds 1 divided by Odds 2.
The Odds Ratio approximates the relative risk and gives you an idea of the strength of
association. For rare events, the odds of a rare event is equal to the risk of rare event
occurring. However, it must be remembered that this does not mean the association seen is causal, i.e. an exposure with a high odds ratio for a disease does not necessarily mean that the exposure causes the disease.

49
Q

Vaccine efficacy

A

protective effect of a vaccine
reduction in disease incidence among people who have been vaccinated compared to disease incidence in those unvaccinated

50
Q

What are the steps of the surveillance process (6)?

A
  1. Planning and system design
  2. data collection
  3. data analysis
  4. interpretation of results of analysis
  5. dissemination & communication of information
  6. application of information to public health programs and practice
51
Q

Issues/barriers in surveillance

A

incomplete data
non standardised data
overlapping/changing categories
loss of data
duplication of data (multiple recording systems)
not incentivised
not comparable e.g. cases of covid between countries due to different testing etc

52
Q

What is a case definition in surveillance

A

what criteria would you use to define a case
Clinical criteria vs microbiological criteria
Not the same as a diagnosis

53
Q

Examples of data sources in surveillance

A

reports from clinicians
lab reports
screening
primary care reporting e.g. sentinel GPs
Death certification
surveillance units e.g. British paediatric surveillance unit
enhanced surveillance (e.g. TB, meningitis)
International surveillance

54
Q

What is the purpose of surveillance

A

Detection of any changes in a disease
Track changes in disease
Detection of new diseases
monitoring and evaluation of prevention & control measures
to aid prioritisation decisions

55
Q

How to explain surveillance data

A

need to look at trends because the actual numbers are unreliable because:
only a proxy measure - not every case detected/reported
Spurious/artificial - failing to notify, notifying wrong
changes in diagnostic methods
changes in attention of the observer
change in observer
random variation
Is it a true outbreak? Or is it seasonal variation etc.

56
Q

Types of surveillance systems

A

Passive
Active
Enhanced
Sentinel

57
Q

what is passive surveillance

A

most surveillance systems
e.g. routine lab/clinician notifications of disease to a surveillance center
surveillor doesnt do anything - the data comes to them
degree of incompleteness
often get very little information about the case

58
Q

What is active surveillance

A

used in situations where complete reporting is required
requires negative reporting also
e.g. for serious/highly contagious disease; monitoring of vaccine failure etc.
Expensive & time consuming - have to contact hospitals/clinicians to ask about cases etc.
Usually only done over a short period of time

59
Q

What is enhanced surveillance

A

Form of active surveillance (but less active)
usually limited to a specific area, time period and disease type for a specific purpose. Health units are required to report cases of diseases that would not normally be routinely monitored.
Often provide incentives

60
Q

What is sentinel Surveillance

A

Incentivise some sentinel sites to report information – e.g. some GP practices etc. extrapolate from those clinics. Works best for common diseases - more likely to miss rarer conditions

61
Q

What can surveillance be of

A

disease
determinants of disease
animal and bird reservoirs

62
Q

What are complex adaptive systems?

A

System of thinking where you can’t understand the system by looking at individual actors - sees healthcare as a dynamic process

63
Q

What are the 3 core characteristics of a complex adaptive system

A
  1. heterogenous agents (e.g. people, organisations, pathogens, animals etc.)
  2. agents interact with each other and evolve their behaviour over time
  3. interactions lead to a pattern called emergence - where the network of actors behave in difficult to understand ways.
    Emergence disguises cause and effect in positive and negative ways.
    e.g. ant colonies
64
Q

Integrated Disease Surveillance and Response

A

aims to integrate multiple categorical surveillance and response systems - linking surveillance, laboratory & other data with public health action.
Example: WHO/AFRO IDSR guidelines combine event based & indicator based framework with disease priority framework and one health approach to zoonotic/vector born disease

65
Q

Event based surveillance

A

detect outbreaks, using official and unofficial reports, need to verify reports meet specific case definition (most credible when supported with labs).
Can be reported early, even before been to Dr (because informal); can be used anywhere; used for all PH events involving potential disease including with unknown cause

66
Q

Indicator based surveillance

A

detects outbreaks, define disease trends, seasonality, burden, risk factors
Reports of cases from health providers (drs, labs etc.). –> usually credible as HCPs told to only report those that meet case definition (but most credible supported by lab).
Timescale: reported after patient has sought medical attention (so can be delayed); only used where there is healthcare infrastructure & willing HCPs; usually only used for known diseases

67
Q

IDSR Framework categories of diseases based on priority for surveillance

A
  1. Epidemic-prone diseases/conditions/events that require immediate reporting (can be passive or active) - case-based identification using standard case definitions for high-priority diseases. e.g. acute haemorrhagic fever syndrome, anthrax, bacterial meningitis, cholera etc.
  2. Diseases targeted for eradication or elimination (may be part of case based strategies or may have dedicated eradication programmes) e.g. Buruli ulcer, bacterial meningitis, leprosy, malaria, measles
  3. Other major diseases/events/conditions of PH importance e.g. HIV, TB, Malaria, viral hepatitis, adverse events following immunisation
68
Q

Why do you get significant osscilation in incidence over time

A

population wide immunity - after 1 wave people either die or become immune, then as a few years pass you get new population (e.g. babies, migrants) and loss of immunity - so then you get another spike (cyclical pattern of infection)

69
Q

Reasons for poor vaccine uptake

A

Mistrust of authority (particularly within minority groups)
Misinformation
Lack of scientific literacy

70
Q

What is an epidemic threshold line used for

A

e.g. to authorise use of antivirals for influenza - outside of flu season you can’t use antivirals (economic and clinical reasons - outside of flu season/epidemic levels it is unlikely that it actually flu over another virus)

71
Q

What is cryptosporidium and what does it cause

A

intracellular parasite - biggest cause of non viral diarrhoea

72
Q

Typical age of incidence of cyptosporidium

A

peak age of incidence: 1-5y
marked reduction over 35y

73
Q

Transmission & Risk Groups for Cryptosporidium

A

Faeco-oral transmission
- Person-person spread
nurseries, food handlers, animal contact, MSM.
Occupational: vets, animal handlers, farm workers
Common in lamb & calf diarrhoea - transmitted in surface run off water - so incidence can be seasonal and related to rainfall
Waterborne transmission:
- oocysts are resistant to chlorination & many disinfectants - unboiled tapwater, swimming pools

74
Q

Cryptosporidium reservoir for infection

A

GI tract of animals & humans

75
Q

Clinical manifestation of cryptosporidium

A

Self limiting in most, chronic in immunodeficient & AIDS.
Low infectious dose
Symptoms: watery diarrhoea lasting 2-4 days, abdominal cramps, fever, vomiting, anorexia.
Likelihood of recurrence: autoinfection

76
Q

Management of cryptosporidium cases

A

Enteric precautions (hand washing, don’t use alcohol hand rub, hygiene etc., gown and glove)
Exclusion until 48 hours after first normal stool
Avoid using swimming pools for 2 weeks after first normal stool
Immunocompromised should boil drinking water

77
Q

What to do if water standard breached (cryptosporidium)

A

Info: when & where was sample; no. of oocysts per 10L, results of viability testing; source of the affected water; how was water treated; distribution area of water supply; any problems with water supply; any recent changes in treatment/source of water; how fast does water travel through distribution area; history of sampling/previous outbreaks

Options for action:
1. take no action
2. Convene incident management team: give advice to special groups, enhanced surveillance for human cases, request alternative source of water, boil water notice

78
Q

Examples of international surveillance

A

Morbidity & Mortality Report (CDC)
Global Networks e.g. GOARN
International collaborations: EISS (european influenza surveillance scheme), EU-IBIS (EU Invasive Bacterial Infections Surveillance), Enter-net, Pro-MED (programme for monitoring emerging diseases)

79
Q

International Health Regulations

A

Updated in 2005.
WHO member states are required to notify WHO for certain diseases.
Health related rules for international trade and travel
Health organisation: measures for deratting, disinfecting, disinsecting ships etc.

80
Q

What are the IHR notifiable diseases

A

Always notifiable: small pox; poliomyelitis due to wild type poliovirus; human influenza caused by new subtype; SARS.

PHEICs:
H1N1 Influenza (2019-2010)
Polio (2014-present)
Ebola
Zika Virus
Covid-19
MPox

81
Q

What is a PHEIC?

A

Public Health Emergency of International Concern
extraordinary event which is a public health risk to other states AND potentially requires a coordinated international response

82
Q
A

Communicable Disease Control MPH (10 decks)

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