DIMACS

European demographic and movement data for modelling

Steve Leach, Phil Sansom, Iain Barrass, Ian Hall

Microbial Risk Assessment

Centre for Emergency Preparedness and Response

Health Protection Agency, UK

October 2008

Spatially Structured Models?

Not always required/useful?Depends on the question(s)

Applications –

• Better understanding spatial aspects of the dynamics of some diseases • Planning realistic interventions – spatial targeting of control strategies

Enhanced data –

• Numerical (demographic, resident populations, working populations, population movements)• Geographic data – analysis and visualisation purposes (boundaries).

Scale & Extent – ?

Depends on the question, the scenario & the infectious agent’s epidemiology

Example National Extent - Smallpox

Speed/Extent of National Spread?How might we best control an outbreak at National level?

Dependencies?Numbers initially infectedTransmissibilityEfficacy of case finding & contact tracingSafety (Deaths) of vaccine

Mass Vaccination Middle Ground Targeted Controls?

Requires a spatially explicit model a more local model reasonable choice

Extent = UK?

Motivation – Historical Outbreak Data: Smallpox

Kerrod E, Geddes AM, Regan M, Leach S (2005) Surveillance and control measures during smallpox outbreaks. Emerg Infect Dis. 11:291-7.

• Liverpool 1902/3• Edinburgh 1942

Hall IM, Egan JR, Barrass I, Gani R, Leach S (2007) Comparison of smallpox outbreak control strategies using a spatial metapopulation model. Epidemiol Infect. 135:1133-44.

Modelling Impacts of Different Intervention Strategies - Some Spatially Localised

VVO SCTS 1111111

VVVV STS 1111

CTTC OV1)(1

ULVU ETTE 1)(1 TLVT ETTE 1)(

UPULU PEP 11 TPTLT PEP 1121

IPI IUP111 QPPQ QTPUP

111

QIR QI11 )( Tpv VVRD

TLOT ECV 12

11

VVP SV 11

tCN

tStStT m

m

Vmmm

US

P

PI

I

ITS PC

RIC

RCC

Modelling - Metapopulation Models

Smallpox - Modelling and Tracking Potential Epidemics Over Space and Time

Beowulf Cluster

Within Patch dynamics Between Patch dynamics

Spatial spread

Spread of disease away from seed in London

Smallpox outbreak

Infected districts three weeks after a covert release of smallpox in London

Eo Itrigg Qdelay*

Vaccine Fatality Rate

0 1 2 5 10

10 0 - - - - -

10 0 2 3 7 7

50 0 1 1 1 4

100 0 0 3 9 9 9

10 0 3 5 5 5

50 0 1 1 2 12

250 0 0 1 1 9 9

10 0 1 2 7,8 8

50 0 1 1 1 24

1000 0 0 0 0 1 12

10 0 0 1 1 12

50 0 0 1 1 1

• With low numbers of index cases, district mass vaccination holds as an optimal strategy with increasing values of Itrigg.

• Baseline interventions are only optimal with low numbers of index cases and when interventions are implemented immediately; unlikely unless the release is overt.

• Nationwide mass vaccination is only optimal for large numbers of index cases and conservative assumptions regarding the vaccine fatality rate.

Some Results

Good National Data - UK

• Reliable• Coherent

• Base demographics• Regular population movements

Data Requirements

Census + Surveys

Describe England, Wales, Scotland according to 2001 Administration Regions

Counties and UAs

142 (67 in 1991)

Districts 434

(459 in 1991)

Wards

10420

99680729692822644170112160406240610

SC

17649895

6613533408804291744519516301193NE

4042089908

751693168319271981015731446819NW

318221627669873

46915381654274808546930YH

1692568531989855

6322962497236882286995WA

1038325773639779858

391971487013825861248WM

1413929921393115799871

7026065245012343SW

1271133286807411074632659686

67412454952276EM

1246129524310869526048359440

7137674719

8SE

15477398322194526316163654389380

625287

7EE

9348201148673012952401303

772799782

92GL

SCNENWYHWAWMSWEMSEEEGL

Work patchH

ome

patc

h

Contemporary population movement data - Commuting

Still To Be Integrated Systematically

• “More Random” population movements National Surveys• Tourism• Shopping• Business• Pleasure• Etc.

Data Requirements

Population Movements – Extent Individual European Countries

Origin–Destination data linking homes and workplaces have been identified for:

• Denmark

• France

• United Kingdom

Other data sets may exist for other countries.

International/European Models

But when planning for the course of a disease in one country or region, it may be necessary to consider the impacts both from and to the surrounding area.

However, it may not be necessary to model the entire region in the same level of detail as the area of primary interest.

Nevertheless some international data at some spatial resolution is going to be required

Example – Pandemic Influenza

International Spread European Perspective, National Importation Scenarios (Surveillance), Geographic Spread, Local epidemics vs. National Epidemic

International Air Transport Data

International Passenger Survey

District based UK model

Experience of Setting up a Data Warehouse

Data from many sources collected and integrated for modelling through projects MODELREL, INFTRANS & FLUMODCONT.

• sub-country,

• country,

• European

• international extents

Some of this data is free and can be easily shared.

Some data is relatively expensive.

Challenges – Spatial Structured Models

One basic data requirement the resident population of each geographic region to be modelled.

The geographic regions for which population counts are most often recorded are geo-political regions (e.g. administrative regions), these regions pose a variety of challenges:

- Several different and non-nested, geographies

- Irregular Shapes

- Uneven distribution of population

European Data

Eurostat – The NUTS System

Eurostat established the NUTS system in order to provide a single uniform breakdown of territorial units for the production of regional statistics for the European Union.

NUTS is a hierarchical system which seeks to equalise the average population of regions within a country at any given level.

Level Minimum Maximum

NUTS 1 3 million 7 million

NUTS 2 800,000 3 million

NUTS 3 150,00 800,000

European Level Census Data

Detailed demographic data is available from Eurostat at NUTS 3 level, dividing the EEA into nearly 1,500 regions, key statistics include:

• Population by sex, 5 year age group, marital & cohabitational status

• Active population by sex, 5 year age group and status

• Households by sex, 5 year age group, status, type & size

Data are mostly complete for the EU but some gaps remain.

Data are free to use.

More Detailed European Census Data

Eurostat holds LAU 2 or commune level 2001 Census data normally only available to the Commission. This divides the EEA in to over 110,000 regions. Key statistics include:

• Population by sex & 10-15 year age groups

• Active population by age group

• Residential housing by status

Data is mostly complete for the EU but:

• some gaps remain

• not always coherent with boundary data

• not necessarily freely available.

European Census Data – Administrative Boundaries

Digital administrative boundaries compatible with NUTS 3 data are available free from Eurostat at a scale of 1:3,000,000.

Digital administrative boundaries compatible with LAU 2 data are available from EuroGeographics at a scale of 1:100,000

But at a substantial cost

European Census Data - CORINE

JRC has disaggregated the Eurostat commune level census data over the 100m grid of the CORINE land use dataset.

• Population counts are exact at commune level

• Analysis of sub-commune data for the UK reveals inaccuracies

• Aggregated to 1km or similar, accuracy should exceed comparable datasets

Data are complete for EU27.

Data are free to use.

International “Census” Data –Landscan

The LandScan Dataset comprises a worldwide population database compiled on a 30”x30” latitude/ longitude grid.

Census counts (at sub-national level) were apportioned to each grid cell based on likelihood coefficients, which are based on proximity to roads, slope, land cover, nighttime lights, and other information.

LandScan has been developed as part of the ORNL Global Population Project for estimating ambient populations at risk.

But data costs for non-academic groups.

o

o

o

Belfast

BangorNewtownabbey

Kells

Moira

Larne

Comber

Bleary

Lurgan

Antrim

Dundrum

Gilford

Dromore

Mossley

Crumlin

Lisburn

Ardglass

Annahilt

Millisle

Crossgar

Holywood

Ahoghill

Banbridge

Newcastle

Drumaness

Kircubbin

Craigavon

Craigavad

Dundonald

Ballymena

Whitehead

Carryduff

Killyleagh

Saintfield

Ballygowan

Donaghadee

Portavogie

Portaferry

Seapatrick

Maghaberry

Magheralin

Ballycarry

Moneyreagh

Ballyclare

Rathfriland

Downpatrick

Newtownards

Ballywalter

Waringstown

Greenisland

Cullybackey Broughshane

Randalstown

Castlewellan

Ballynahinch

Hillsborough

Templepatrick

Carrickfergus

International “Census” Data –GRUMP

The GPW and GRUMP data sets provide worldwide population databases compiled on a 30”x30” latitude/longitude grid, including:

• Population

• Population Density

• Settlement Points

• Urban Extents

The data is less heavily modelled than LandScan and therefore has lower effective resolution.

Data are free to use.

International Census Data –other sources

World populations at national level may be obtained for free from a number of sources including:

• CIA World Factbook

• United Nations

No other single source of detailed contemporary socio-demographic data or sub-national populations and compatible geo-data.

Possible to obtain sub-national population data for the super–states of China and India, and other larger countries such as the US.

National Population Movements other than Commuting

Travel surveys conducted in individual countries may yield distributions of:

• Distances

• Frequencies

• Timings

for trips disaggregated by:

• Age

• Sex

• Purpose

• Method of transport

Eurostat collects air passenger origin–destination data for Europe including:

• Domestic and international flights

• Data by month, quarter or year

• Data by country, region or airport

• Some charter flights

Data are free to use.

European Population Movements

International Population Movements

The United Nations World Tourism Organization’s Yearbook of Tourism Statistics contains origin–destination data on an annual basis for around 240 countries, including:

• Arrivals at national borders

• Arrivals at accommodation establishments

• Overnight stays in accommodation establishments

• All modes of transport

Negligible Cost

International Population Movements

The International Civil Aviation Authority’s On-Flight Origin–Destination database includes:

• Data by city pair

• Data by quarter or year

• Only scheduled flights

Some Cost.

International Population Movements

The International Air Transport Association’s On-Flight Origin–Destination database includes:

• Data by city, country or region

• Monthly data

• 70% of scheduled passengers

• Data may only represent ~50% of passenger traffic

Data costs are likely to be high.

Comparison across DatasetsCountry pairs

ICAO – 350M trips – 1,100 connectionsIATA – 400M trips – 1,100 connectionsWTO – 850M trips – 10,500 connections

International Models – Problems & Solutions?

No coherent or poor data currently for:

Some types of regular and more random cross-border population movements in Europe

Regular and more random international population movements worldwide

Locally worse(?) for places elsewhere in the world

Ignore the Gaps!?

Approximations?

• Gravity-type models• Diffusion• Combinations

• Population density• Distance• Socio-economic factors• Length of shared borders

Explaining data?

Predicting /Estimating Future?