Using GIS as a Tool for Investigating Outbreaks
Adrienne Dunne
CET, HPA East Midlands
15th May 2007
Outline of this mornings session
Demo of ESRI ArcGIS software
While focusing on work undertaken on Legionnaire’s disease by a student on placement with the HPA EM, during early 2006.
ESRI ArcGIS
ArcGIS is an integrated collection of GIS software products that allow visualisation, management, creation and analysis of geographic data.
There are 3 ArcGIS applications:
• ArcMap or ArcView - is used for all mapping and editing tasks as well as for map based analysis. *
• ArcToolbox – is used for data conversion and geoprocessing (integrated into ArcMap)
• ArcCatalog - is the application for designed for browsing, managing and documenting geographic data.
http://www.esriuk.com
Overview of ArcView
Switch to ArcView for demo
ArcView in Layout view
ArcView in Data View
Zoom features
Pan
Identify feature
Investigating Layer properties
In layer properties the transparency and symbology can be set
Labels can be added using default settings e.g each feature labelled in same way, although can alter fonts, size etc
Or labelling can be defined using the labelling manager and SQL queries.
Labels can be converted to annotation and manipulated as graphics.
Legionnaires Disease
Legionnaires' disease, is a rare form of pneumonia.
It takes its name from the first known outbreak which occurred in a hotel that was hosting a convention of the Pennsylvania Department of the American Legion in 1976.
Disease is most often contracted by inhaling mist from water sources.
Caused by bacteria, that is widely distributed in the environment
Disease fatal in 5% to 15% of cases.
Source: BBC website
Legionnaires Disease – Outbreak Barrow-in-Furness 2002
Multiple deaths linked to leisure centre air conditioning
A HPU investigation of Legionnaires in the East Midlands
HPU notified of case of Legionnaires (usually via microbiology lab)
Patient will be interviewed (HPA or LA) – towards identifying locations the patient had been 2 weeks prior to onset.
• Particular interest in any contact with water (i.e. plumbing, water features, whirlpool/ spa pools, car washes etc)
Environmental Sampling (including the home)
The scientific bit (?):
• Can a source be identified and is there a link to any other case (either current or historic)?
• Partnership working is important• National reporting of data (national and European surveillance)
Student Project – Defining the Problem
When investigating cases of legionnaires’ HPU staff need to:
• Access information on potential sources
• Access current/ historical case information
• Identify potential sources
• Identify potentially linked cases
Student Project - the Study
• Pilot project• Partnership with one Local
Authority – Ashfield DC• Collected data on potential
sources• Collected data on cases
Student Project – Data Collection
Collection of data- Liaison with Ashfield District Council and Health Protection Unit North
Potential sourcesCase Data
Student Project – Mapping and Manipulation of the Data
Back to ArcView
Adding data
Data can be added by dragging and dropping from ArcCatalog
Add data button
Importing tables from database and adding XY data
Using symbology to define data
In the layer properties you can define how you want data displayed
Using Selection Features
Select by location – select potential sources within 500m of a case location
Using Selection Features
Select by attribute – selection of ‘cooling tower’ sources that are within 500m of a case (using selection on previous slide)
Buffering – Using ArcToolbox
Single or multiple buffers can be drawn using the Analysis Tools (Proximity) within ArcToolbox.Once completed Arcview will ask if the data is to be added to the map.
Clipping and extracting data
Using the Analysis Tools (Extract) within ArcToolbox, you can clip features from one layer based on another i.e. extract sources within the created buffer areas
Potential Benefits of Using GIS to investigate Outbreaks
Stores historical data in one place in an easy to access system.
Visual representation of cases and potential sources
Allows you to see relationships, patterns, or trends
Changes in data are reflected instantly in the GIS
No local knowledge is necessary for use
Can run queries on the data to aid investigation
Considerations in making GIS use a reality
Number of cases
Co-ordination within the HPA
Liaison with local authorities
Accuracy of data
Security of Information
Accessibility
The need for GIS
Project work has identified that GIS as a useful tool
No of cases in East Midlands Aug- Oct 2006
The need for GIS
Growing interest in the practical use of GIS within HPA/ HPU
However, need resources to develop fully. Especially time to keep datasets current.
Understanding of what GIS can’t do – not a panacea of all problems!
Better than relying on memory (?)
Questions?
Contact details:
Health Protection Agency – East Midlands
29 Bridgford Road
West Bridgford
Nottingham
NG2 6AU
T: 0115 981 5675
F: 0115 981 5500
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