Introduction for Basic Epidemiological Analysis for Surveillance Data
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Transcript of Introduction for Basic Epidemiological Analysis for Surveillance Data
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Introduction for Basic Epidemiological Analysis for
Surveillance Data
National Center for Immunization & Respiratory Diseases Influenza Division
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Strategic Information
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What Does Strategic Information Mean?
Generating information and knowledge to influence policy making, programmatic action and research
• Which viruses are circulating, where, when, who is affected?
• Contribute to vaccine selection• Determine intensity and impact of activity• Detect unusual events
oUnusual virusesoUnusual syndromesoUnusually large/severe outbreaks
Understand the impact of influenza to guide policy and resource decisions nationally, regionally, globally
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What do we mean by strategic
information?
DATA
INFORMATION
KNOWLEDGE
ACTION!
Data demand generation
Analysis
Understanding
Application
Increasing emphasis on data use and utility
Assessment
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Considerations: Data Collection & Analysis
Data for action must be timely
Analysis does not need to be complex to be useful
Know your data!
Feedback to data providers is critical
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Considerations: Timeliness Timely analysis can mean:
• Use of preliminary results in order to convey data quickly
• Rapid response to unusual events• Implementation of prevention and control
efforts• Situational awareness
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Considerations for Analysis Surveillance data analysis does not have to be complex
to be useful – analyses that can be updated frequently & quickly are often sufficient
• Often the simple messages are the most important and effective during an influenza season:o Currently circulating viruseso Geographic spread of activityo Increases & decreases in activityo Who is being affectedo Detection of unusual events – large outbreaks, unusual
severity; unusual viruses Responsibility to use all data collected
• Does not all need to be used in routine reports• Full analysis may be done at less frequent intervals• Responsibility to follow up on signals
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Know Your Data All datasets are different – let your analysis & decision
making plans guide your collection of a dataset
• Consider how much data is needed for a stable output
• Which sites have the biggest impact
There is no one way to do analysis BUT some basic principles of surveillance analysis are key to a global understanding
Analytic methods can be developed and enhanced over time
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Examples of Analysis & Reporting
Weekly reports:
• Percent SARI/ILI flu positive, by population, hospitalizations, consultations, region
• Comparison to previous seasons
• Number of SARI/ILI patients tested & proportion positive
• Number of sentinel sites reporting
• By age group
• Observation of circulating types & subtypes
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Weekly Analysis
Allows detection of signals & rapid response to follow up of signals
• Where is the increase occurring? Single site? Multiple site?
Are there increases in other surveillance data – laboratory positives?
• Are you receiving specimens?• Is the signal due to another pathogen?
Contact site submitting data for more information Make sure you understand & can explain the data
you are reporting Again, a glance at a picture gives a good
understanding of current activity, problems, monitoring of reporting
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Example: US Weekly Outpatient ILI Report
Monitor Influenza-like Illness
• >3000 healthcare providers in 50 US states
• Mix of practice types
• >25 million patient visits each year
• Subset provides clinical specimens
Regularly Reporting Sites: 2009-2010
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Example: US Weekly Outpatient ILI Report
Quick graphical presentation of ILI activity provides a picture of what is happening now, how it compares to baseline and to previous seasons
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Example: US Weekly Outpatient ILI Report
Same data, by state, allows us to see regional trends
Again, a glance at a picture gives a good understanding of current activity
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Example: US Weekly Cumulative Rate of Hospitalizations
Quick understanding of severity by age group – who is requiring hospitalization?
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Example: US Weekly Pediatric Deaths
Very simple, easy to update graphic of the number of pediatric deaths compared with past season
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5
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2007
-40
2007
-46
2007
-52
2008
-06
2008
-12
2008
-18
2008
-24
2008
-30
2008
-36
2008
-42
2008
-48
2009
-01
2009
-07
2009
-13
2009
-19
2009
-25
2009
-31
2009
-37
2009
-43
2009
-49
2010
-03
2010
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-15
2010
-21
2010
-27
2010
-33
2010
-39
2010
-45
2010
-51
2011
-05
2011
-11
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-17
2011
-23
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2011
-35
Week of Death
Num
ber
of d
eath
s
2007-08Number of Deaths
Reported = 88
2008-09Number of Deaths
Reported =133
2009-10Number of
Deaths Reported=282
2010-11Number of Deaths
Reported=116
Deaths Reported Current Week Deaths Reported Previous Weeks
Date Influenza A (2009 H1N1)
Influenza A (H3N2)
Influenza A (Subtype Unknown) Influenza B Total
# Deaths CurrentWeek – 39 0 0 0 0 0
# Deaths SinceOctober 1, 2010 30 21 20 45 116
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Example: WHO Weekly Report for the Eastern Mediterranean Region
Data source: FluNet (www.who.int/flunet). Global Influenza Surveillance and Response System (GISRS) Data generated on 27/03/2013
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Annual Reporting Epidemiologic surveillance: SARI & ILI:
• In-depth description and summary of annual trends in SARI data collected by week unable to be analyzed and updated on a weekly basis:o Ageo Gendero Comorbiditieso Vaccine coverageo Fatalities
Virologic surveillance:o How many positive flu testso Type and subtype of circulation viruseso Distribution of viruses by age and severity
Vaccine data:• Understand match between circulating viruses & vaccine
strains• Vaccine coverage by age/risk groups• Antiviral resistance
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Conclusions These are simply examples:
• Your analysis plan depends on your data & the message you want to convey; these are critical considerations when you develop your database: develop a plan first
None of the examples shown include complex analysis• Counts, %, cumulative rate• These simple analyses allow for effective presentation of
data, whether in one week or for the whole year
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Conclusions However, even simple analysis requires
upfront preparation• Receipt of data requiring little or no cleaning• Streamline as many tasks as possible
o Easy data entry or uploado Predefined querieso Graphic templates
Remember that surveillance systems are built over time
• Constantly monitor your data, make improvements as needed, fine tune your analysis
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Thank you!Questions?