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Extrapolating the real number of H1N1 cases in the US

wotan

wotan

Well-known member
After having looked through http://www.cdc.gov/h1n1flu/pubs/pdf/FluView_Week17.pdf, I was beginning to wonder, do the CDC have a method they use to take the number of cases of influenza officially reported and extrapolate out a realistic number of actual cases and deaths. They can't honestly assume they are getting all the cases.

If there is a method using these numbers to estimate the real number of cases, can we start getting a better feel for the real situation in the US over the coming weeks as more of these reports are released?
 
Re: Extrapolating the real number of H1N1 cases in the US

of course there is.
It would be useful and informative if they publish such estimates.

Best in a regularly updated short table on their webpage
and not hidden in long texts.

Other experts,bloggers,journalists may join and critisize,discuss,publish their own estimates
 
Re: Extrapolating the real number of H1N1 cases in the US

I guess I should have said, does anyone outside of the CDC know what formula they use to determine the number of actual cases. :/
 
Re: Extrapolating the real number of H1N1 cases in the US

I don't know if there is one formula that could be applied to the US. Testing practices, capacity and capability vary among states.
 
Re: Extrapolating the real number of H1N1 cases in the US

They definitely aren't counting all the cases. Many states have stopped testing except in a few special situations like hospitalization.

The CDC recommendations are, except for high risk people, to ignore the flu until / unless symptoms become "severe". They say don't test, don't give antivirals, don't report, don't hospitalize, and don't even visit the doctor (until it becomes severe). That is different from what they were doing two weeks ago.

So today's numbers are really meaningless. Soon they will probably stop reporting them.

Eventually they will estimate what percentage of the population was infected via blood tests, to see who developed antibodies.
 
Re: Extrapolating the real number of H1N1 cases in the US

In fairness to the question, and the above retort which is all accurate, one might, for ones own illustrative purposes use Mexico as the model, both in "estimating " total case numbers, and to a lesser extent, create a best guess time line. I think one could feel that the following calculation - "although meaningless" as to its un-empiricalness -would be a good faith attempt.

Mexico:

Probable cases to date: 36,000
Confirmed cases to date: 2,509

1. Figure out the the multiple differential between the confirmed and probable - write it down

2. Take the Confirmed US cases - and multiply that number by the differential Mexican case multiple.

That should give you a pretty good picture of the US - IF THE US (which it may or may not) had its Patient 0 - on the same date as Mexico -

_________________________________________________________________


But in fairness to the "conservative numbers fudge factors" - one would need to presume Mexico is at least 4 weeks ahead of the US as to the emergence of Patient 0 - so today would need to be thought of as APRIL 13 and not MAY 13TH - and then you can use any one of several sources to "guess" where Mexico was on April 13th - and reduce your US numbers accordingly -

Its not perfect - but it could pass for a guesstimation as to the US - and still be "way low" as the kids today say -

Then - you can come up with the speed that we "seem to be ahead of Mexico as to Ro - guess at a rate of speed from the records - state by state - ie, the rate of tranmission etc -

Again, not perfect, will be a lower number than reality, and will be based on at least "professionally provided statistics" - (whether high or low - right or wrong)
 
Re: Extrapolating the real number of H1N1 cases in the US

PS - as to my above formula:

The other thing is: THEY (CDC, STATES ETC) ARE NO LONGER even testing for conformed cases - so maybe, a dartboard and a hand-held calculator and an imaginary number as the multiple - would be a more scientifically sound methodology.
 
Re: Extrapolating the real number of H1N1 cases in the US

Therefore,

Just take the MEXICO differential multiple and multiply it times the US confirmed cases - and "call it day."
 
Re: Extrapolating the real number of H1N1 cases in the US

I do so hope that Dr Niman, will see # 6,7, and 8 and provide his Will Rodgers, Mark Twain wit - and science acumen to said formula - and provide us his opinion.
 
Re: Extrapolating the real number of H1N1 cases in the US

I am bumping this thread because I believe that the estimated number of cases is very important in calculating when to make true last minute preparations for the pandemic.

The government agencies are not giving us a true picture: 1) they're not testing all the cases now, 2) they're not in my mind giving a strong enough warning, 3) they're fiddling with the definitions in order to bow to civic leaders.

Since this thread started, the CDC has quietly said that the estimated cases could be as high as 100,000 in the USA versus approximately 5000 cases at that point. I've seen variations on this report, some saying half of those cases are regular influenza and the other swine flu. In either case, those reports are starting to filter in to the main stream media outlets. Still, swine flu is not headline worthy news. In my own city, it's buried on the back pages.

I live in one of the states that doesn't have a high count of verified flu cases. I was surprised recently that a school with a flu case in my state decided to stay open, in spite of the recent NYC school that has begun the shut the schools down. It seems like it's a judgment call by local authorities. Weird and in my view irresponsible.

How are we to know when to truly prepare....when the bodies start accumulating in the streets? I would think some gonzo journalist would jump on this story.

Dr. Niman ,to his credit, has estimated in another thread that the true number of cases of swine flu is 1 or 2 orders of magnitude greater than the CDC's recent projection. I wonder what would be a logical means of estimating the real caseload with a fairly high confidence level. There must be some scientific means of doing projections.

Dr. Niman's Flutracker map has not been adjusted to include the 100,000 number yet.

Earlier I found several websites which attempted to project the true number of cases. I think that all of those websites have not adjusted their graphs since the 100,000 number was released. See these old links:
http://www.physorg.com/news160327953.html
http://www.cavemanforecaster.com/2009/05/latest-h1n1-swine-flu-tracking-charts.html
http://rocs.northwestern.edu/projects/swine_flu/

To date, I have not found anyone who has fulfilled a graph of the real case numbers.
 
Re: Extrapolating the real number of H1N1 cases in the US

http://www.cdc.gov/flu/weekly/
http://www.cdc.gov/flu/weekly/weeklyarchives2008-2009/weekly15.htm
http://www.cdc.gov/flu/weekly/weeklyarchives2008-2009/weekly49.htm

in week 15 they tested 2449 specimens, 151 of which were positive for seasonal flu
in week 18 they tested 12202 specimens, 755 of which were positive for novelflu,699 for other flu
in week 49 they tested 2585 specimens, 72 of which were positive
until week 49 they had tested 31394 specimens, 507 of which were positive

cumulative for the season until week 15 they had tested 183839 specimens, 25925 of which were positive.

Per season an estimated 10% of the population is infected with flu.
Looking at the graph - we are in tail almost where we were in week 49 in the head

so 215000 specimens in total and 26400 positives expected for the season ignoring novel flu strain.

72 of these 26400 positives were in week 49, that's 0.27% , or ~80000 people in USA
so expect ~80000 people with seasonal flu for week 18 too and the same amount of people
with novel flu in USA
 
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Re: Extrapolating the real number of H1N1 cases in the US

And the CDC has been throwing out 100,000 as the likely number.
 
Re: Extrapolating the real number of H1N1 cases in the US

and niman seems to think it's 10-100 times higher
 
Re: Extrapolating the real number of H1N1 cases in the US

well to show hidden stats they need to add a few more colors for 25K cases, 100K cases, 250K cases. 1M cases... etc

We have a Russian show up in Egypt and get quarantined, but of course there are no cases in Russia...

many country's are starting to have the truth come out thanks to the monitoring in some countries...

Wait until the Haj hits full swing and Saudi Arabia has 50,000 pilgrims in quarantine from countries around the world... and that doesn't count the 25000 that will slip under the radar with no temperature, rub elbows with a few hundred thousand people before heading back home...

Yep we're all pretty lucky that we have WHO watching over us to keep the world safe.
 
Re: Extrapolating the real number of H1N1 cases in the US

80% of confirmed flu in USA is Mexflu meanwhile according to CDC

that makes an estimated ~300000 people in USA infected with Mexflu
 
Re: Extrapolating the real number of H1N1 cases in the US

The latest transcript from the CDC hasn't been released since it is being broadcast as we speak. The main speaker is reporting that 1 in 20 cases are the estimates that the CDC is using. We may be able to calculate a model close to what they themselves are constructing. For example there are 6.552 cases as of 11 am Eastern on 05/22/09. So perhaps there are 131,040 cases in theory?
 
Re: Extrapolating the real number of H1N1 cases in the US

OK, so using that number from a week or two ago, and assuming a CFR of something close to season flu (0.1% is the number I have stuck in my head) then we should have ~100 deaths in the USA.. Using the CFR of 0.8%) that the "official" number point towards then we should have 800 deaths.

At some point numbers like that should become visible. And if Niman's assessment of the number of cases is correct then it should start showing up a lot sooner.
 
Re: Extrapolating the real number of H1N1 cases in the US

Fatalities take time. It seems that most people who die had become sick two or more weeks beforehand, and sometimes there is a further delay in reporting deaths. If there are now 400,000 cases, there may have been only 25,000 cases two weeks ago. At least 16 people have died who first became sick more than 2 weeks ago. Also, maybe only half of those who became sick over 2 weeks ago with a case that will prove fatal have died yet (and been discovered and reported). Thus, perhaps 1/800 of cases prove fatal. Moreover, it those figures are right (and who knows?), the death rate among middle-aged people is much higher, since cases among middle-aged people are the minority by far (perhaps 10-15% of cases are among people 30-60 years old), while most deaths are in that category (at least 10 of the 16 who became sick over 2 weeks ago). If those figures are right (and who knows?), the death rate among people 30-60 years old could be 0.005%. That's extremely high for middle-aged people. Of course, the death rate could become lower with prompt and effective treatment. And it could become higher when hospitals are overwhelmed and can't treat people as well.
 
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