Posted by
Phil Henshaw-2 on
Mar 31, 2007; 12:42pm
URL: http://friam.383.s1.nabble.com/One-of-my-projects-tp523626p523629.html
Doug,
Did you not answer my question just because it seemed obvious or
something? The other questions and your other answers all seemed very
thoughtful, but didn't address mine. I'm thinking the use of the tool
would include helping people in the learning process of finding what is
actually working during the experience of an epidemic. Every pathogen
and every public health initiative will have different growth dynamic
characteristics, and sometimes very small differences will have large
effects, especially because of relative lag times of divergence and
response. I was commenting, I guess, on the difference between a
universal general model of epidemic spread and response and the
particular event process of an individual epidemic and the creative
adaptation an effective response requires.
Phil Henshaw ????.?? ? `?.????
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-----Original Message-----
From:
[hidden email] [mailto:
[hidden email]] On
Behalf Of Douglas Roberts
Sent: Friday, March 30, 2007 5:45 PM
To: The Friday Morning Applied Complexity Coffee Group
Subject: Re: [FRIAM] One of my projects
A few of you have asked questions about the the EpiSims-Grid project, so
I'll try to answer them here, in roughly inverse order that they were
received:
From: Paul Paryski:
For someone like me who rarely works with such complex models this is a
very interesting discussion. Out of my ignorance a couple of questions
have popped into my aging synapses:
-does the model include mutation and other adaptations by diseases?
No, we have only simulated one pathogen at a time, to date, and it does
not mutate.
-are you going to study past massive epidemics to see what patterns are
applicable (bio mimicry and incidence of natural immunity, cultural
practices)
Yes, we have done this fairly extensively. Lots of data exists from the
1918 pandemic flu outbreak, for example.
-who will make the political choice to use the info/models when the time
comes?
Good question. See my response to Laura Mac's questions bleow.
>From Laura MacNamara:
Being someone who studies people who use models, I'm curious about how
you guys are relating to your user community. Who are the intended
analysts (the ones that you hope know what you're doing)? At what
point do you guys start engaging them? Do they treat your simulation as
black box?
Our last study was commissioned by a high-level consortium of
Department-level representatives -- Dept. of State, Dept. of Treasury,
Dept. of Homeland Security, Dept. of HHS, and the office of the White
House. The purpose of the study was to help them identify relative
measures of effectiveness regarding what intervention strategies would
provide the most benefit in the event of a pandemic flu outbreak.
Examples of intervention strategies that were modeled included
1. Self-isolation (staying home when symptomatic)
2. Social distancing (telecommuting, scheduled trips to the store
with minimal contact to other shoppers, in general minimizing physical
proximity to other people) during an outbreak
3. Closing down schools and non-critical workplaces
4. Treating critical infrastructure workers with anti-viral
treatments (remember -- it was a pandemic being simulated, there were no
vaccines)
5. etc.
The intent was to help government officials develop a response plan in
the event of an outbreak. I was quite impressed with the expertise with
which the leader of the study, the White House representative, directed
the study. He was one of the most knowledgeable and intelligent of any
of the customers that I have aver worked with. The simulations used in
the study were most definitely not treated as black boxes. Rather, the
strengths and weaknesses of each of the three models were thoroughly
explored.
The consortium of users approached the leader of the MIDAS project and
requested our participation on the project last summer, at which point
we immediately engaged with them to develop an experimental design.
>From Robert Holmes:
Fair enough: big simulation answers some questions, small simulation
answers others. So what are the specific questions that a big
epidemiological simulation can answer? It can't be anything too
predictive ("ohmigod, New York has just fallen to small pox. Which city
is next?") because that depends (I'd guess) on something that is
unsimulatable ("errr.... dunno. Kinda depends which flight the guy with
small pox got onto"). What are the questions that can only be answered
with a big model?
EpiSims was by far the most detailed of the three models used. It is an
individual-based ABM in which the second-to-second movements of every
individual in the 8.6-million population city were modeled for 60
consecutive 24-hour days. Further, each individual was fairly
completely characterized demographically -- race, inccome, marital
status, number of children, etc. Also, family household structures are
created by EpiSims, in which the same adults and children come back to
the same household every day.
This level of detail allowed us to run experiments on specific
demographic subsets of the population that were not possible with the
other models. For example, we ran a series of experiments for which
social distancing was less effective among lower income people, because
they could not afford to stay home -- they had to work. These runs were
compared to runs where all working members of the population had the
same compliance when social distancing measures were imposed.
Another example of experiments that were conducted with EpiSims that
could not be achieved with the other models: we ran several experiments
in which the imuno-response of lower economic segments of the population
was less effective in resisting the pandemic virus then for those more
affluent members of the population. The reasoning being that poorer
people have less access to health care.
Remember, the intent of these studies was to establish a relative
effectiveness ranking determination of various intervention strategies
for future use establishing a response strategy in the event of a
pandemic outbreak. The intent was *not* to model "ohmigod, New York has
just fallen to small pox. Which city is next?" types of human behavior
in response to an outbreak.
I hope this addresses some of your questions. Thanks for your interest!
--Doug
--
Doug Roberts, RTI International
droberts at rti.org
doug at parrot-farm.net
505-455-7333 - Office
505-670-8195 - Cell
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