Overestimating cases, underestimating case fatality rate

As I’ve argued before, estimates of case fatality rate based on influenza-like illness are wrong. This is because lots of viruses cause similar symptoms to influenza. Even allergies can be mistaken for a mild case of the flu. Remarkably, CBS News did not take the assurances of the CDC on this issue on faith and actually did some investigative reporting. Here is what they found:

From CBS News, October 21, 2009 [hat-tip, Pixie]

If you’ve been diagnosed “probable” or “presumed” 2009 H1N1 or “swine flu” in recent months, you may be surprised to know this: odds are you didn’t have H1N1 flu.

In fact, you probably didn’t have flu at all. That’s according to state-by-state test results obtained in a three-month-long CBS News investigation.


We asked all 50 states for their statistics on state lab-confirmed H1N1 prior to the halt of individual testing and counting in July. The results reveal a pattern that surprised a number of health care professionals we consulted. The vast majority of cases were negative for H1N1 as well as seasonal flu, despite the fact that many states were specifically testing patients deemed to be most likely to have H1N1 flu, based on symptoms and risk factors, such as travel to Mexico.

CBS had to go to extraordinary lengths to get this information because the CDC would not provide the necessary data:

On Aug. 4, CBS News asked the CDC for e-mail communications to states and other documents regarding the guidance and its rationale. When CDC did not provide us with the documents, such as state-by-state numbers prior to halting testing and tracking, we filed a Freedom of Information request with the Department of Health and Human Services (HHS). More than two months later, the request has not been fulfilled.


The CDC did not response to questions from CBS News for this report.

It’s not surprising that the CDC did not release the information that CBS was trying to obtain. The fact that there was no huge number of “missing mild” cases that would inflate the denominator for calculating the case fatality rate suggests a much more lethal virus than the CDC has told the public to expect. Indeed, their own internal study, leaked to cryptome, suggests that we will experience a severe pandemic if it is not mitigated.

And the CDC, by telling people over and over again that this is a mild pandemic and that they were already likely infected have made mitigation much more difficult. If you’ve already been infected and the symptoms were mild, why get a vaccine? The CDC has played right into the hands of the anti-vaccine agitators who can point to an inconsistent, opaque government agency. Everyone can tell the CDC is hiding something. The problem is, most people have not yet figured out that what the CDC is hiding is that we are in the middle of 1918-type pandemic. And if they don’t start telling the truth, we are going to experience the full weight of a severe pandemic without the benefit of mitigation.

Oh what a tangled web we weave,
When first we practise to deceive!

Sir Walter Scott


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