exponential

while the total number of cases grows only linearly,
the number of clusters or cases in clusters seems to grow exponentially - almost redoubling each year.

ask experts for their subjective
panflu death expectation values
and report the replies

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by: gs @ Mon Nov 20, 2006 at 09:37:09 AM UTC

[ Parent ]

exponential illusions

If 1 in 1000 chickens infects a human, and if the rate of chicken infections is going up exponentially, the rate of human infections will also rise exponentially even though it is still 1000 chickens to infect one human and the transmissibility to or between humans remains unchanged. 

It is possible to have the appearance of exponential spread in humans when it is in fact an exponential spread in chickens that is the problem.

medical information provided is for discussion purposes only and should not be construed as medical advice. if you believe you have a medical problem, consult your practitioner.

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by: Lisa the GP @ Mon Nov 20, 2006 at 09:47:02 AM UTC

and the aparent increase in cluster size

How would you interpret the aparent increase in cluster size?  Could that be due to "more or better information"?  Could it be a function of the increase in cases in chicken?

Of course, no one is saying that we should wait for perfect information.  But it looks like many people are in fact waiting for more information before they act.

You arm yourself to the teeth just in case.  You don't leave the gun near the baby's hand.

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by: lugon @ Mon Nov 20, 2006 at 10:05:11 AM UTC

[ Parent ]

PS

I don't mean to imply only chickens.  It could be any carrier animal.  My point is only that we cannot just look at the human numbers without looking at the animal numbers which may account for the increases in human cases.

medical information provided is for discussion purposes only and should not be construed as medical advice. if you believe you have a medical problem, consult your practitioner.

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by: Lisa the GP @ Mon Nov 20, 2006 at 09:51:41 AM UTC

More on illusions

As Lugon and Lisa mentioned there can be a lot of explanations as to why there seem to be more clusters.  Back in '03,  BF wasn't so widespread geographically as it is now.  Also, I don't know how much more or less seriously the cases were investigated back then.  IOW did a lot of mysterious deaths simply not get investigated whereas now they are more aggressive in checking potential cases near areas of sick birds?  I think it's inconclusive at this point unless we know that investigational protocol was the same back then as it is now. 

There can be psychological and policy reasons for an apparent increase in clusters.  I'm pretty sure there are countries that took a while to pay attention to avian influenza.  Are the newer countries that are being affected more willing to publicize cases that might be viewed as clusters, like Turkey and Egypt, or do they all have the same level of caution.  Has WHO upped the awareness to different countries individual health organizations? 

IMHO there are statistically too few cluster cases per in the relatively few countries reporting to really draw conclusions when the issue is so multi-variate in it's inputs.  It will take a while after WHO generates a very specific monitoring and reporting standard, AND after every country gets over their specific reasons for hiding things to protect their economy or good name (which will never happen).  Most likely, it would take a much larger number of clusters, and countries affected consistently for a few years before we could tell.  And PI might not wait to give us good statistics.  The excellent graphs put there by Florida RN are very compelling, and definitely suggest something is going on.  But in stats you are looking for a 95% confidence interval. This to me seems better than a 50/50, but it's not 95.  It's something in between, and I think there need to be more undeniable circumstances seen in multiple places to draw any definitive conclusion.

I do LOVE the graphs though.  To me they are definitely compelling and tell me it's something to watch and I wish I knew WHO was investigating the specific question:  Based on what appears to be a larger incidence of clusters, can we say for sure that H5N1 is effectively becoming easier to transmit H2H?  I'm sure they are (occasional posts here and there in news threads would seem to suggest as much) and it would be great to get a focused blow-by-blow on that particular investigation.

Meteorologist in Florida!?!  Now we're talkin'!!!

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by: Tempest @ Sun Dec 03, 2006 at 13:00:24 PM UTC

[ Parent ]

Florida Girl not Florida RN...thanks Florida Girl n/t

Meteorologist in Florida!?!  Now we're talkin'!!!

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by: Tempest @ Sun Dec 03, 2006 at 13:22:20 PM UTC

[ Parent ]

more detected clusters ...

We all agree: more detected clusters may or may not mean more clusters.

Let's imagine this hypothetical situation:

- At time A there were 100 clusters and we detected 20.

- At time B there were 100 clusters and we detected 40.

It looks like an increase from time A to time B, which is worrying.

But I'd be more worried about the (hypothetical) (100-20)+(100-40)=140 undetected clusters.

And it could also be that at time B we have 200 clusters and we detect 40.

Or whatever.

The real numbers may differ, but that's the idea: there are clusters we're not detecting.  If they are less now it doesn't change the whole picture much, I think.  Or does it?  What do we think?

You arm yourself to the teeth just in case.  You don't leave the gun near the baby's hand.

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by: lugon @ Thu Dec 28, 2006 at 20:51:27 PM UTC

[ Parent ]

Either way

Even if it is an increase in chicken (or other animal) speading the virus.  Bottom line, the more people that get the virus, (regardless of how) there is more of an opportunity for the virus to change to a H2H transmittable form.

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by: indypokerboy41 @ Thu Dec 28, 2006 at 19:08:49 PM UTC

[ Parent ]

Thoughts on the cluster data...

I did not realize there has been conversation going on about the cluster information.  My thoughts on the availability of information about clusters are simply this….  In 2003, H5N1 was not widespread; it was limited to a smaller area of Asia, it was relatively unknown to the local doctors in what to look for in relation to symptoms, and the reporting mechanisms did not have as much urgency as they do today. 

That being said… as time progressed, information became more available, the area expanded into Europe. The urgency DID become a little higher, so reporting mechanisms became better. (Maybe not as good as we wish it to be… ;)  )

It may contribute to the increase in clusters.  The information that is contained in the graphs is simply the information that has been available in a reliable source i.e. WHO, Pro-Med, Peer-review studies, etc.  Suspect cases are included if the case is cited as “probable”, “suspect”, or otherwise “labeled”.  These cases are mostly the cases that died without being tested, but are acknowledged as being possible “index” cases (or other such designation).

It is a little like “The Hawthorn effect”:
  “In essence, the Hawthorne Effect can be summarized as "Individual behaviors may be altered because they know they are being studied." This means that the act of measurement, itself, impacts the results of the measurement. In science, dipping a thermometer into a vial of liquid can affect the temperature of the liquid being measured. In the same way, the act of collecting data, where none was collected before creates a situation that didn't exist before, thereby affecting the results.

http://www.everythin...

Hopefully soon, I will finish this last quarter of the year, and update the graph.  Any and all are welcome to look at the raw data to validate the information.  Let me know if your find any discrepancies.

Lisa the GP made a good point in that… the more “chickens” (or other animal) that has H5N1, the more likely there will be more cases in humans.  Dr Nabarro, or Dr. Webster, (or someone) said much the same thing this past spring. It makes sense.

So. Are there really more cases and clusters?  Or are we just finding and reporting more because we know what to look for.  I think, it is a little of both.  I also think, we are not seeing all of them…. And we may be missing reporting some that are coming up a false negative.

Those are my thoughts on why the cluster sizes appear to be increasing….

Never believe that a few caring people can't change the world. For, indeed, that's all who ever have. ~ Margaret Mead

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by: FloridaGirl @ Fri Dec 29, 2006 at 02:20:26 AM UTC