Unit 4: Overview of Public Health Surveillance

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Unit 4 Overview of Public Health Surveillance
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Warm Up Questions Instructions

• Take five minutes now to try the Unit 4 warm up
  questions in your manual.
• Please do not compare answers with other
  participants.
• Your answers will not be collected or graded.
• We will review your answers at the end of the
  unit.

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What You Will Learn

• By the end of this unit you should be able to
• describe the components of a surveillance system
• define sentinel surveillance, laboratory-based
  surveillance and case definitions
• define incidence and prevalence

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What is Surveillance?

• Systematic collection of information on a
  specific disease or other health-related event
• Must occur on an ongoing basis with sufficient
  accuracy and completeness for data analysis
• Utilisation of information for disease prevention
  and control

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Information Loops

• A surveillance system is an information loop or
  cycle that involves
• healthcare providers
• public health agencies
• the public

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Figure 4.1. Flow of Surveillance Data
Collection
Dissemination, Utilisation
Collation
Analysis and Interpretation
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Surveillance Terms

• Universal case reporting a surveillance system
  in which all cases of a disease are supposed to
  be reported
• Sentinel surveillance a surveillance system in
  which reports are obtained from certain
  facilities or populations
• Laboratory-based reporting a surveillance
  system in which the reports of cases come from
  clinical laboratories instead of healthcare
  practitioners or hospitals

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Terms Related to Surveillance, Cont.

• Case definition the clinical and laboratory
  characteristics that a patient must have to be
  counted as a case for surveillance purposes
• Prevalence the proportion of persons in a
  population who have a disease or condition at a
  given point in time
• Incidence the number of persons who newly
  develop a disease or condition within a specified
  period of time

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Terms Related to Surveillance, Cont.

• Passive surveillance a system in which data
  generated without solicitation, intervention or
  contact by the health agency carrying out the
  surveillance. Other agencies initiate reporting.
• Active surveillance the organization conducting
  surveillance initiates procedures to obtain
  reports

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Table 4.1. Relationship Between Disease and Case
Definition
True Disease True Disease
Case Definition Present Absent Total
Met a b ab
Not Met c d cd
Total ac bd N
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Additional Surveillance Terms

• Sensitivity the ability of a case definition or
  laboratory test to predict true disease (a/(ac))
• Specificity the ability of a case definition or
  laboratory test to predict absence of true
  disease (d/(bd))

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Additional Surveillance Terms, Cont.

• Positive predictive value proportion of persons
  meeting a case definition, having a positive
  test, that have true disease (a/(ab))
• Negative predictive value proportion of persons
  not meeting a case definition, having a negative
  test, that do not have true disease (d/(cd))

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Past Approaches

• Duplication of efforts and resources
• Delays in reporting and identification of
  outbreaks
• Lack of dissemination and feedback to the local
  level
• Lack of integration of training and surveillance
  activities

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Common Problems with Past Surveillance Systems,
Cont.

• Limited evaluation of programmes
• Inadequate involvement of laboratories
• Incomplete reporting and lack of supervisory
  support

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Integrated Disease Surveillance (IDS)

• Integrates priority communicable disease
  surveillance activities at the district level
• Provides support for training and supervision
• Full-time district-level staff dedicated to
• monitoring health events in the community
• mobilising community action
• encouraging national assistance
• accessing regional resources
• Resources combined to collect information at each
  level

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IDS Goals

• Strengthen the capacity of countries to conduct
  effective surveillance activities
• Integrate multiple surveillance systems so that
  forms, personnel and resources can be used more
  efficiently and effectively
• Improve the use of information for making
  decisions
• Improve the flow of surveillance information
  between and within levels of the health system

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IDS Goals, Cont.

• Improve laboratory capacity in identification of
  pathogens and monitoring of drug sensitivity
• Increase the involvement of clinicians in the
  surveillance system
• Emphasise community participation in detection of
  and response to public health problems
• Strengthen the involvement of laboratory
  personnel in epidemiologic surveillance

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Examples of Priority Communicable Diseases for IDS

• Epidemic-prone diseases
• Cholera
• Yellow fever
• Diseases targeted for eradication and elimination
• Polio
• Neonatal tetanus
• Other diseases of public health importance
• Malaria
• STIs

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In Summary

• Surveillance is the collection of data relevant
  to public health, which can then be analysed to
  guide prevention and treatment programmes.
• Sentinel surveillance involves the collection of
  more detailed data from a smaller sample of sites
• Laboratory-based reporting occurs when case
  reports come from laboratories instead of health
  facilities.

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In Summary, Cont.

• Prevalence is the proportion or number of persons
  in a certain population who have a particular
  disease.
• Incidence measures new infections during a
  specific time period.

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Warm Up Review

• Take a few minutes now to look back at your
  answers to the warm up questions at the beginning
  of the unit.
• Make any changes you want to.
• We will discuss the questions and answers in a
  few minutes.

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Answers to Warm Up Questions

• 1. What is the name of the system that integrates
  priority communicable disease activities at the
  district level with support for training,
  supervision and resources?

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Answers to Warm Up Questions

• 1. What is the name of the system that integrates
  priority communicable disease activities at the
  district level with support for training,
  supervision and resources? Integrated Disease
  Surveillance

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Answers to Warm Up Questions, Cont.

• 2. Which of the following terms indicates the
  number or proportion of persons in a population
  who have a disease at a given point in time?
• a. sensitivity
• b. prevalence
• c. negative predictive value
• d. none of the above

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Answers to Warm Up Questions, Cont.

• 2. Which of the following terms indicates the
  number or proportion of persons in a population
  who have a disease at a given point in time?
• a. sensitivity
• b. prevalence
• c. negative predictive value
• d. none of the above

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Answers to Warm Up Questions, Cont.

• 3. True or false? One-time cross-sectional
  surveys are valid methods of HIV/AIDS
  surveillance.

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Answers to Warm Up Questions, Cont.

• 3. True or false? One-time cross-sectional
  surveys are valid methods of HIV/AIDS
  surveillance. False

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Answers to Warm Up Questions, Cont.

• 4. Match the following terms with their
  definitions
•  

___ sentinel surveillance a. surveillance system in which the reports of cases come from clinical laboratories as opposed to healthcare practitioners or hospitals
___ laboratory-based reporting b. clinical and laboratory characteristics that a patient must have to be counted as a case for surveillance purposes
___ case definition c. surveillance system in which reports are obtained only from certain selected facilities and populations
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Answers to Warm Up Questions, Cont.

• 4. Match the following terms with their
  definitions
•  

_c_ sentinel surveillance a. surveillance system in which the reports of cases come from clinical laboratories as opposed to healthcare practitioners or hospitals
_a_ laboratory-based reporting b. clinical and laboratory characteristics that a patient must have to be counted as a case for surveillance purposes
_b_ case definition c. surveillance system in which reports are obtained only from certain selected facilities and populations
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Answers to Warm Up Questions, Cont.

• 5. Which of the following terms indicates the
  number of persons who newly develop a disease
  within a specified time period?
• a. specificity
• b. positive predictive value
• c. incidence
• d. none of the above

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Answers to Warm Up Questions, Cont.

• 5. Which of the following terms indicates the
  number of persons who develop a disease within a
  specified time period?
• a. specificity
• b. positive predictive value
• c. incidence
• d. none of the above

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Small Group Discussion Instructions

• Get into small groups to discuss these questions.
  
• Choose a speaker for your group who will report
  back to the class.

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Small Group Reports

• Select one member from your group to present your
  answers.
• Discuss with the rest of the class.

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Case Study Instructions

• Try this case study individually.
• Well discuss the answers in class.

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Case Study Review

• Follow along as we go over the case study in
  class.
• Discuss your answers with the rest of the class.

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Questions, Process Check

• Do you have any questions on the information we
  just covered?
• Are you happy with how we worked on Unit 4?
• Do you want to try something different that will
  help the group?

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