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

E: cet@hpa.org.uk