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
<[EMAIL PROTECTED] cc:
us.edu.sg> Subject: Re: AI-GEOSTATS: Dengue &
population
13-07-2001 22:31
On Fri, 13 Jul 2001 [EMAIL PROTECTED] 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
\ / \ / [EMAIL PROTECTED]
N C
| || Currently
CH3 O Graphics Lab
School of Computing
National University of Singapore
The Real Part of Coffee [EMAIL PROTECTED]
----- 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-P�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: [EMAIL PROTECTED]
************************************************************
* To post a message to the list, send it to [EMAIL PROTECTED]
----- Forwarded by Basil LOH/ENV/SINGOV on 16-07-2001 09:15 -----
"Richard Hoskins"
<[EMAIL PROTECTED] To: <[EMAIL PROTECTED]>
> cc:
Sent by: Subject: RE: Dengue & population
[EMAIL PROTECTED]
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: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of [EMAIL PROTECTED]
Sent: Friday, July 13, 2001 1:36 AM
To: [EMAIL PROTECTED]; [EMAIL PROTECTED];
[EMAIL PROTECTED]; [EMAIL PROTECTED];
[EMAIL PROTECTED]
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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