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AI-GEOSTATS: SUM: Dengue & population

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  • Basil_LOH@ENV.gov.sg
    Hi everyone, Thank you so much for your great responses. Below is a sum of a SUM on what I got. But first, here s my original question. ORIGINAL QUESTION: Hi
    Message 1 of 1 , Jul 15 6:18 PM
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      Hi everyone,
      Thank you so much for your great responses.

      Below is a sum of a SUM on what I got. But first, here's my original
      question.

      ORIGINAL QUESTION:
      Hi list members,

      I am new to geo/spatial statistics and I don't have any expert spatial
      epidemiologist in my country. So I thought I'd run through what I have done
      with you all, and check whether I am on the right track. If anyone has any
      better ideas, please feel free to let me know too!

      I am working on the following questions:
      How can I test the hypothesis that most of the dengue cases are located
      where most of the population are?
      How can I test the hypothesis that significantly more dengue cases are
      located in the east than in the west of my country?
      How can I detect if there are any clustering or any other spatial trends of
      dengue in relation to population?

      In my Arcview GIS 3.2, I have a polygon layer of population according to
      postal sectors (83 polygons with sizes ranging from 0.3 km(superscript: 2)
      to 33 km(superscript: 2)). I also have a point layer of dengue cases.

      What I've done so far:
      Correlated number of dengue cases with population in each postal sector
      polygon.
      Correlated number of dengue cases with population density (i.e.
      population/ area) in each postal sector.
      Correlated dengue morbidity rate (i.e. no. of cases/ population) with
      population in each postal sector.
      Correlated dengue morbidity rate with population density in each postal
      sector.

      What more can I do?

      Thanks very much in advance. Best wishes.

      Basil
      Vector Control & Research Dept
      Singapore


      ----- Forwarded by Basil LOH/ENV/SINGOV on 16-07-2001 09:15 -----

      Nicholas
      Lewin-Koh To: Basil LOH/ENV/SINGOV@SINGOV
      <kohnicho@comp.n cc:
      us.edu.sg> Subject: Re: AI-GEOSTATS: Dengue & population

      13-07-2001 22:31






      On Fri, 13 Jul 2001 Basil_LOH@... wrote:
      Hi,
      Actually there are a few of us here at NUS.

      >
      > Hi list members,
      >
      > I am new to geo/spatial statistics and I don't have any expert spatial
      > epidemiologist in my country.

      Actually there are a few of us here at NUS.

      > I am working on the following questions:
      > How can I test the hypothesis that most of the dengue cases are located
      > where most of the population are?
      > How can I test the hypothesis that significantly more dengue cases are
      > located in the east than in the west of my country?
      > How can I detect if there are any clustering or any other spatial trends
      of
      > dengue in relation to population?

      What you are looking for is tests of case clustering and small area
      estimation.
      There is a very nice package for R (or Splus if available) called Splancs
      that has a lot of the procedures you might be looking for.

      You might want to
      a) test for significant clusters of Dengue cases.
      b) Fit a Spatial poisson model on the counts of dengue per postal area
      (probably over dispersed due to lots of 0's)

      c) test environmental covariates against incidence

      d) fit a model to determine risk of contracting the disease (hazard rate)

      You have the luxury of using either point pattern type approaches or
      lattice models on the postal areas.

      You can call me if you want more advice at
      874-6559

      Nicholas

      >
      > In my Arcview GIS 3.2, I have a polygon layer of population according to
      > postal sectors (83 polygons with sizes ranging from 0.3 km(superscript:
      2)
      > to 33 km(superscript: 2)). I also have a point layer of dengue cases.
      >
      > What I've done so far:
      > Correlated number of dengue cases with population in each postal
      sector
      > polygon.
      > Correlated number of dengue cases with population density


      CH3
      |
      N Nicholas Lewin-Koh
      / \ Dept of Statistics
      N----C C==O Program in Ecology and Evolutionary Biology
      || || | Iowa State University
      || || | Ames, IA 50011
      CH C N--CH3 http://www.public.iastate.edu/~nlewin
      \ / \ / nlewin@...
      N C
      | || Currently
      CH3 O Graphics Lab
      School of Computing
      National University of Singapore
      The Real Part of Coffee kohnicho@...

      ----- Forwarded by Basil LOH/ENV/SINGOV on 16-07-2001 09:15 -----

      "Richard M
      Webb" To: Basil LOH/ENV/SINGOV@SINGOV
      <rmwebb@usgs. cc:
      gov> Subject: Re: AI-GEOSTATS: Dengue & population

      14-07-2001
      00:07





      Basil,

      I hope the following reference can offer you some guidance and/or ideas.

      Morrison, A.C., Santiago, Marilyn, Rigau-PĂ©rez, J.G., and Reiter, Paul,,
      1998, The
      Transmission of Dengue fever in Puerto Rico: an epidemiologic approach
      using a
      geographic information system: U.S. Geological Survey Water-Resources
      Investigations Report 98-4119, 86 p.

      Regards,

      Rick Webb

      ************************************************************
      Richard MT Webb
      USGS, WRD Telephone: 303-236-5025
      Box 25046, MS 413, DFC Fax: 303-236-5034
      Denver, CO 80225-0046 Email: rmwebb@...
      ************************************************************


      * To post a message to the list, send it to ai-geostats@...

      ----- Forwarded by Basil LOH/ENV/SINGOV on 16-07-2001 09:15 -----

      "Richard Hoskins"
      <healthmaps@... To: <waphgis@...>
      > cc:
      Sent by: Subject: RE: Dengue & population
      WAPHGIS-owner@...
      ington.edu


      14-07-2001 03:49
      Please respond to
      waphgis






      Basil: I think one very effective way to get the information you need is
      to
      use a spatial scan statistic approach. Your data is made for it. You do not
      need to test the hypothesis of E vs W, and of course

      likely, there are more cases where there are more people - I suspect the
      mossies like areas where
      there is lots of food(people).
      I think you need to know where the rates are higher than anywhere else, if
      the idea is to deal with those areas first.
      Also it can tell you where areas are lower than expected and give an easy
      to
      understand way to determine if the rates are really elevated or not.

      The spatial scan statistic can be easily calculated. The background is
      http://www.sph.umich.edu/~lestberg/GeoMed/Scan/ScMain.htm

      http://sun2539.sph.umich.edu:2000/geomed/stats/kullscan/scan.html

      http://sun2539.sph.umich.edu:2000/geomed/stathelp/advisor.html

      http://dcp.nci.nih.gov/bb/SaTScan.html has free software

      and there is a commercial product now which does cluster calculations

      http://www.terraseer.com/clusterseer.html which has a whole lot of cluster
      tests bundled in one place.

      A link directly to ArcView http://www.phrl.org/REGS/Order.htm

      Dick Hoskins
      WA State Dept of Health



      -----Original Message-----
      From: WAPHGIS-owner@...
      [mailto:WAPHGIS-owner@...]On Behalf Of Basil_LOH@...
      Sent: Friday, July 13, 2001 1:36 AM
      To: waphgis@...; ai-geostats@...;
      fnpbb@...; getis@...;
      owner-health-gis@...
      Subject: Dengue & population



      Hi list members,

      I am new to geo/spatial statistics and I don't have any expert spatial
      epidemiologist in my country. So I thought I'd run through what I have done
      with you all, and check whether I am on the right track. If anyone has any
      better ideas, please feel free to let me know too!


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