Establish a Surveillance System

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First question: Why do you want to

conduct surveillance?

• Detect emerging pathogen, reappearance of an old one, or outbreaks.

• Monitor behavior of existing pathogens

• Monitor trends in epidemiology: risk factors, age groups, seasonality, etc.

• Measure disease burden: absolute (incidence) or relative to other diseases

• Evaluate impact of an intervention

• It’s helpful to actually write down the objectives

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The answers will determine:

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Will the system be active or passive?

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Will it be a sentinel indicator-based system or an event detection system

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What diseases will you measure?

 Will it be more than one? based on syndromic  Surveillance and/or laboratory testing?

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Will this be a new system or will you add on to existing system?

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What population will you monitor?

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Decisions to Make

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What data will you collect?

 Decide first, what the major public health questions are.

 With a limited sentinel system, can also get risk factor data such as age, medical conditions, vaccination status, etc.

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Who will collect, analyze and report data?

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Who will interpret data and take action?

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How will report be shared and to whom?

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How will system be monitored?

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Support Needed

•

Administrative

 Laws •

Political

 Ministry of Health

 Medical community •

Resources

 Funding

 Staff

 Training

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SETTING UP THE SYSTEM

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What are the necessary bits?

•Data:

 Source  content

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Steps to establishing a new system

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Data sources

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Identify what data to collect

 Decide how it will be used, what decisions will be based on the data.

 Limit the amount of data to what is actually going to be useful.

•

Collect data systematically

 Data collection forms

 Case definitions

•

Train reporters

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Case definition

•Standardization helps compare apples to apples •Can have different levels of certainty:

 Confirmed, probable, suspect

 Surveillance case definition may differ from clinical diagnostic definitions:

e.g. ILI

•Components: diagnostic criteria (lab and clinical); who, where, when  Is laboratory confirmation required?

 Who: is there an age group of interest? E.g. the pediatric influenza mortality

surveillance system. If all age groups, how do you aggregate?

 Where: may be especially important for disease burden estimates when a specific catchment area is under surveillance.

 When: some systems may run seasonally, e.g. influenza.

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Case definition example

• Influenza-like Illness:

An acute respiratory infection with:

measured fever of ≥ 38 C°; and cough;

with onset within the last 10 days.

• Severe acute respiratory infections (SARI)

An acute respiratory infection with:

history of fever or measured fever of ≥ 38 C°; and cough;

with onset within the last 10 days; and requires hospitalization

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Case reporting form

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Site Selection Criteria

•Representativeness: what population needs monitoring? (consider HIV vs. Influenza)

 General hospitals may be better than referral centers for some diseases but not others  Consider variations in climate, ethnicity, risk factors.

•Logistics:

 Need to be able to transmit data and clinical specimens

•Patient volume:

 Site should get sufficient number of cases to be meaningful.

•Ability to determine denominator:

 Can you estimate the proportion of total cases that are actually reported/tested?  Can you estimate the size of the catchment population?

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How many sites, how many specimens?

• Number of sites depends somewhat on variety of disease ecology

 Are there differences in climate?

 Is there much diversity in the population?

 Is there a region or population of special interest?

• How many can you afford?

• What portion of total numbers reported are likely to be truly the disease of interest?

• Number of specimens/cases is not related to population size but rather prevalence of the disease.

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Influenza surveillance

Italy

Rwanda

Albania

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Reporting

• Lab based or clinic/hospital

• Mechanism to report: electronic, web, telephone, mail

 Technology is not the answer. Get the system working first!

• Immediate reporting of priority diseases:

• Lowest level that reports

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• Laboratory reports and data summaries back to reporting facility

• IHR secure channels

• Meetings and conferences

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Monitoring and Evaluation

• Basic indicators should monitor timeliness, completeness, and validity of data

 However indicators don’t tell the whole story

• Watch for aberrations in the data

 Don’t assume you know the reason

• Keep system small enough that monitoring can assure the quality of the data

• Periodic audits important to really dig deep

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• Consistency in reporting is critical since the goal is to observe trends

 All must report the same thing  All must report regularly

• Don’t get ambitious – a little data goes a long way towards understanding a problem

 Aim for representativeness rather than volume

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Thank you

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