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

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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

Case Definition Present Absent Total

Met a b a+b

Not Met c d c+d

Total a+c b+d N

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Additional Surveillance Terms

Sensitivity – the ability of a case definition or laboratory test to predict true disease (a/(a+c))

Specificity – the ability of a case definition or laboratory test to predict absence of true disease (d/(b+d))

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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/(a+b))

Negative predictive value – proportion of persons not meeting a case definition, having a negative test, that do not have true disease (d/(c+d))

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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:

 

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___ 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

Answers to Warm Up Questions, Cont.

4. Match the following terms with their definitions:

 

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_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

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.

We’ll 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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