OUTBREAK INVESTIGATION Flashcards

1
Q

Levels of Diseases:
The amount of a disease that is usually present in a community
Observed but not necessarily the desired level
Regarded as the expected level of disease

A

Baseline

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2
Q

Levels of Diseases:
A disease that occurs infrequently and irregularly
Occurs occasionally at irregular intervals

A

Sporadic

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3
Q

Levels of Diseases:
The constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area
Has a stable pattern of disease occurrence in a population
Constant presence of cases in a certain population

A

Endemic

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4
Q

Levels of Diseases:
The persistently high levels of disease occurrence
Has a stable (relatively high) pattern of disease occurrence in a population

A

Hyperendemic

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5
Q

Levels of Diseases:
An increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area
From endemic to epidemic
Sudden raise in the number of cases

A

Epidemic

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6
Q

Levels of Diseases:
Similar to an epidemic but is often used for a more limited geographic area
Sudden increase in the number of cases which is more than what is usually expected in the population

A

Outbreak

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7
Q

Levels of Diseases:
An aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number maybe unknown

A

Cluster

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8
Q

Levels of Diseases:

An epidemic that has spread over several countries or continents, usually affecting a large number of people

A

Pandemic

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9
Q

ODD MAN OUT:

Epidemic: Occurrence of disease cases or deaths

  1. Limited to specified group of individuals during a short period of time
  2. Constant number of expected cases at a specified place and time
  3. Clearly on excess of normal expectancy (Last, 1988)
  4. Take note of the group; gathered together in a certain place or time
  5. Cases or deaths are more than what is expected at a given time and place
A
  1. Constant number of expected cases at a specified place and time
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10
Q

A if only the first statement is true
B if only the second statement is true
C if both of the statements are true
D if neither of the statements is true

How do epidemics occur?

  1. Agents and hosts are present in adequate number
  2. Agent can not be effectively conveyed from source to host
A

A

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11
Q

ODD MAN OUT:
Factors which may trigger an epidemic:

  1. Recent increase in virulence of agent (Virulence: whether the agent causes severe disease)
  2. Recent introduction of agent into a setting
  3. Persistent health education programs in communities
  4. Enhanced mode of transmission: important
    If fast transmission: fast occurrence
  5. Change in susceptibility of the host response to agent (Susceptibility: lack of ability to resist some extraneous agent)
  6. Factors that increase host exposure
  7. Introduction of agent through new portals of entry
A
  1. Persistent health education programs in communities
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12
Q

Goals of an outbreak investigation:
_____: Guide —> intervention: guide the public health for the intervention that we want to implement

_____: Identify —> source: identify the source of illness or mode of transmission

A

Long term goal

Short term goal

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13
Q

Ways on how outbreaks come to the attention of public health agencies:

A. _______
Organization or structures
Collection, analysis & interpretation of outcome-specific data
Planning, implementing & evaluation of PH practices
B. _______

A

A. Epidemiologic Surveillance System
Organization or structures
Collection, analysis & interpretation of outcome-specific data
Planning, implementing & evaluation of PH practices
B. Direct notification

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14
Q

Reasons for Investigating Outbreaks:
Primary Public Health reason for investigation
Principal considerations:
What is the stage of the epidemic? Are cases occurring in increasing numbers? Is the outbreak just about over?
Important for it will help you in needs assessment or what are the steps that are needed to further do based on the stage of the epidemic

A

Prevention and Control

How much is known about the causative agent, the source, and the mode of transmission of the agent? To be able to stop the outbreak
The decisions regarding whether and how extensively to investigate an outbreak are influenced by the characteristics of the problem itself
Ex: the severity of the illness, the source or mode of transmission, the availability of prevention and control measures

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15
Q

Reasons for Investigating Outbreaks:

If cases are Continuing to occur:
Goal: prevent occurrence of additional cases
Objective: to assess the extent of the outbreak, the size, and characteristics of the population at risk
Important in deciding and implementing the appropriate control measures

A

Prevention and Control

Outbreak appears to be Almost over:
Goal: prevent similar outbreaks in the future
Objective: to identify factors which contributed to the outbreak
In order to design and implement measures that would prevent similar outbreaks in the near future

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16
Q

Reasons for Investigating Outbreaks:
Each outbreak is an opportunity to study the natural history of the disease in question
For a newly recognized disease, field investigation provides an opportunity to define the natural history – agent, mode of transmission, and the incubation period and the clinical spectrum of the disease.

A

Gain additional knowledge or research

Are able to characterize the populations at greater risk: identify specific risk factors
Assessing impact of control measures
Ex: Legionnaires disease in Philadelphia in 1976; Toxic Shock Syndrome in 1980, AIDS in early 1980’s, Eosinophilia-myalgia-syndrome in 1989)

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17
Q

Reasons for Investigating Outbreaks:
Investigating an outbreak requires a combination of diplomacy, logical thinking, problem-solving ability, quantitative skills, epidemiologic know-how and judgment.

A

Training

These skills improve with practice and experience
The investigating team can be composed of a seasoned epidemiologist with trainee/s.

18
Q

Reasons for Investigating Outbreaks:
These concerns sometimes override scientific concerns in the decision to conduct investigation
Concerns are what initial initiates an outbreak investigation

A

Public, political, or legal concerns

Increasingly, the public has taken an interest in ‘disease clusters’ and potential environmental exposures, and has called upon the health department to investigate.
Disease clusters: diseases that occur in a certain geographic area

19
Q

Reasons for Investigating Outbreaks:
An outbreak of a disease (which is targeted by a public health program) may reveal a weakness in that program and provide an opportunity to modify/ strengthen the program’s efforts.

A

Program considerations

Investigating the causes of an outbreak may identify populations which may have been overlooked, failures in the investigation strategy, changes in the agent, or events beyond the scope of the program.
May give an idea on why there is still an outbreak even if programs are implemented, there can be changes in the agent or failure in the implementation

20
Q

Preparation for Field Work can be group into:
Appropriate scientific knowledge, supplies, and equipment; consult regarding epidemic, laboratory specimen collection, storage, and transport

A

Investigation

21
Q

Preparation for Field Work can be group into:

Travel arrangements and travel orders

A

Administration

22
Q

Preparation for Field Work can be group into:

Specific roles and responsibilities

A

Consultation

23
Q

Steps in an Outbreak Investigation:

A
  1. Verify the diagnosis and confirm the outbreak
  2. Define a case and conduct case finding
  3. Tabulate and orient data
  4. Do immediate control measures
  5. Formulate and test hypothesis
  6. Plan and execute additional studies
  7. Implement and evaluate control measures
  8. Communicate findings
24
Q

Categories of Cases:
1. _____: Symptoms characteristic of the agent
Laboratory confirmation of the disease
Lab test and Epidemiologic link
2. ____: Symptoms confirmed
Person has typical clinical features of the disease but without the laboratory confirmation
No lab or epidemiologic link
3. _____: Symptoms are reported but not confirmed
Fewer of the typical clinical features of the disease
No lab or epidemiologic link

A
  1. Confirmed
  2. Probable
  3. Suspected
25
Q

Histogram of the number of cases against onset of the signs and symptoms
Graphical depiction of the number of cases of illness by the date of illness onset
The overall shape of this can reveal the type of outbreak:
Common source: point, continuous, intermittent
Propagated
Mixed

A

Epidemic Curve

Can provide information on the following characteristics of an outbreak:
Pattern of spread
Magnitude
Outliers
Time trend
Exposure and/or disease incubation period

26
Q

Can provide a sense of the magnitude of an outbreak

Additional information can be obtained by stratifying the epidemic curve

A

Outbreak Magnitude

27
Q

Provides information on the time trend of the outbreak based on the following:
Date of illness onset for the first case
Date when the outbreak peaked
Date of illness onset for the last case

A

Outbreak Time Trend

28
Q

Outliers are cases at the very beginning and end that may not appear to be related to the rest of the cases

A
Outbreak Outliers
If they are not errors, they may represent: 
Baseline level illness
Outbreak source
A case exposed earlier than the others 
An unrelated case
A case exposed later than the others 
A case with a long incubation period 
Check to be certain that they are not due to coding or data entry error
29
Q

Common Source:
Cases were all exposed to the same source during a brief period of calendar time
Typically shows a sharp upward slope and a gradual downward slope
Is a common source outbreak in which the period of exposure is brief, and all cases occur within one incubation period:

A

Common Point Source

30
Q

Common Source:

will often cause cases to rise gradually and possibly to plateau/ flatness, rather than to peak

A

Continuous Exposure

31
Q

Common Source:
Brief, sporadic exposure period
Irregular peaks reflect timing and extent of exposure
The gaps between the outbreaks might initially suggest person-to-person transmission followed by an incubation period.

A

Intermittent

32
Q

The classic epi curve for this type of outbreak is progressively taller peaks, one incubation period apart
Spread is from person-to-person and Can last longer than source outbreaks

A

Propagated Epidemic

Disease agent may replicate in a susceptible host as part of the transmission cycle; transmission can be vehicle or vector-borne
May have multiple waves

33
Q

Either same disease introduced separately or different diseases with different incubation periods introduced around the same time

A

Mixed Epidemic

Involve both a single, common exposure to an infectious agent and secondary propagative spread to other individuals (e.g., person to person transmission)
Ex: Many food borne pathogens (Salmonella, typhoid, Hepatitis A) and airborne organism (M. tuberculosis)

34
Q

ODD MAN OUT:
Factors Affecting Duration of An Epidemic

  1. The number of susceptible persons who are exposed to a source of infectious and become infected;
  2. The pace of the health actions conducted as response to the epidemic
  3. The period of time over which susceptible persons are exposed to the source
  4. The minimum and maximum incubation periods for the disease
A
  1. The pace of the health actions conducted as response to the epidemic
35
Q

A special cumulative incidence ( or incidence proportion) that measures the proportion of persons in a population who experience an acute health event during a limited time (e.g., outbreak)

A

Attack Rate

Number of new cases of a health problem during an outbreak divided by the size of a population at the beginning of the period who are at risk of the event

36
Q

Reflect the strength of association between the exposure and the disease under investigation

A

Measure of association (RR-Risk Ratio)

37
Q

The ratio of the number of cases among contacts occurring within the acceptable incubation period following exposure to a Primary Case to the total number of exposed contacts.

A

Secondary Attack Rate

Applicable to orphanages and schools
The frequency of new cases of a disease among the contacts of known patients

38
Q

If the timing of the exposure is known, epi curves can be used to estimate the incubation period of the disease
Time between the exposure and the peak of the epi curve represents the median incubation period

A

Period of Exposure/ Incubation Period for the Outbreak

39
Q

identify the last case in the outbreak and count backwards for the ________ period

A

Maximum incubation period

40
Q

ODD MAN OUT:
Aims of Outbreak Investigation

  1. Describe population size
  2. Determine the cause of the outbreak (the disease detected)
  3. Prevent further spread of the outbreak (the fire fighter)
  4. Educate responsible individuals in the prevention of similar outbreak in the future (the public health educator)
A
  1. Describe population size