From Basil_LOH@env.gov.sg Sun Oct 21 09:29:29 2001
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Subject: Spatial-temporal clustering by chance
To: waphgis@u.washington.edu, METHODS@linux08.UNM.EDU, ai-geostats@unil.ch,
   fnpbb@diamond.mahidol.ac.th, GIS-STATES-OTHER@LISTSERV.CDC.GOV,
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From: Basil_LOH@env.gov.sg
Date: Mon, 22 Oct 2001 00:30:36 +0800
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 10/22/2001 12:27:08 AM
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Hi everyone,

In Singapore, we define a dengue cluster (referring to an outbreak when
dengue fever is spreading contagiously from one person to the next) as at
least 2 cases (points) within 200 m of each other and within 3 weeks of
incidence of each other. With about 2,000 cases so far this year, I have
about about 80 clusters according to this definition.

However, I suspect that the occurence of some clusters (especially the ones
with just 2 or 3 cases) may be by chance, instead of an actual disease
transmission happening. How can I test this? Possibly, a Monte Carlo
simulation of some kind will help. Is there any software out there that can
help to do this? SATScan has got some promising functions, unfortunately it
deals with areal or polygon data and not point data (I think).

Will sum answers.

Thanks for your attention. Cheers.

Basil

.