

Estimating and Predicting Epidemic Behavior for the West African Ebola Outbreak - thadk
http://grantbrown.github.io/libspatialSEIR/doc/tutorials/Ebola2014/Ebola2014.html

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ghshephard
I don't understand how people can model epidemics like this. Isn't the
infection and spread for something like ebola highly variable, and mostly a
function of education and resources?

Unlike the Flu, which is easy to pass on, Ebola is hard to catch, and unlike
HIV, has a fairly brief infectious period. The WHO could, with the assistance
of local government, basically shut down this epidemic in a matter of months
with field hospitals, education, and proper burial/isolation practices.

I'm not sure how you model that kind of response when trying to make future
predictions.

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sytelus
You can sure model pretty much anything _without_ knowing internal variables
and complexities of the system. In fact that's the entire premise of the field
_learning from data_. Of course you need good quality data and in sufficient
quantity.

Your model will almost never be perfect but you can evaluate confidence
intervals by using part of the past data (training set) and making prediction
for events that is not included in that data (test set) and find out how good
is your model. This process is scattered with land mines. People frequently
end up overfitting or do not take in to account variability trends or power
laws or possible "black swans". So all such models you want to take with grain
of salt in any case.

For this particular case, I don't think we have enough data yet to make
predictions with significant confidence. From past epidemics in same region,
it will very likely that this will end without getting out of control. One of
the big deal about current strain is that it doesn't manifest symptoms until
1-3 weeks which gives plenty of time for virus to spread.

One should never discount the power of power law. We are safe only until
tipping point is not researched. I think that tipping point is about 10,000
infected people in a city. If this happens, it would take extreme measures to
prevent spread (something like completely isolating entire countries). But by
that time, virus might have already escaped elsewhere.

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jjoe
"One of the big deal about current strain is that it doesn't manifest symptoms
until 1-3 weeks which gives plenty of time for virus to spread"

""The patients become contagious once they begin to show symptoms. They are
not contagious during the incubation period.""

Source: [http://www.who.int/csr/disease/ebola/faq-
ebola/en/](http://www.who.int/csr/disease/ebola/faq-ebola/en/)

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kryptiskt
> ""The patients become contagious once they begin to show symptoms. They are
> not contagious during the incubation period.""

It still gives them time to diffuse from where they were infected.

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reuwsaat
Thank you for making this. I've been following the outbreak in the news and
searching for something better than repeating quotes from the WHO or
politicians saying everything is going to be fine.

Even if this models isn't 100%, it's better analysis than other easily
accessible analysis I've found. I'm certain it will be of assistance to those
trying to help and needing to understand. It may spur others to do similar
work.

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gwern
It looks like something like a sixth of his writeup is devoted to chains of
MCMC convergence diagnostics. Is non-convergence really that serious an issue
for epidemiological modeling?

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Fomite
Non-convergence can be fairly serious in epidemiological modeling, and crop up
somewhat unexpectedly. Beyond that, it's really easy to produce the trace
plots to check it.

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jamesfisher
> There should probably be a word for uncumulating things, perhaps uncumulate.

Isn't that "differentiation"?

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sdenton4
Yeah, this was my thought, too. "Hey, you re-invented the derivative!" Of
course, it's a discretized derivative, but whatev's.

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aw3c2
What does SEIR stand for? I cannot find it explained anywhere.

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jk4930
Susceptible, Exposed, Infectious, Recovered/Removed.

[http://en.wikipedia.org/wiki/Compartmental_models_in_epidemi...](http://en.wikipedia.org/wiki/Compartmental_models_in_epidemiology)

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aw3c2
Thank you!

