Introduction for Basic Epidemiological Analysis for Surveillance Data
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Transcript of Introduction for Basic Epidemiological Analysis for Surveillance Data
Introduction for Basic Epidemiological Analysis for
Surveillance Data
National Center for Immunization & Respiratory Diseases Influenza Division
Strategic Information
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
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
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
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
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
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
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
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
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
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
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
Example: US Weekly Cumulative Rate of Hospitalizations
Quick understanding of severity by age group – who is requiring hospitalization?
Example: US Weekly Pediatric Deaths
Very simple, easy to update graphic of the number of pediatric deaths compared with past season
0
5
10
15
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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
-09
2010
-15
2010
-21
2010
-27
2010
-33
2010
-39
2010
-45
2010
-51
2011
-05
2011
-11
2011
-17
2011
-23
2011
-29
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
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
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
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
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
Thank you!Questions?