Posted by A reader (h/t MVD) sent me this link to a “CBS News Exclusive,” Study Of State Results Finds H1N1 Not As Prevalent As Feared. As far as I can see the main aim was to raise CBS News’s profile and gain readership. That’s what news organizations do. We hope they do it by good journalism. I think this is an example where the reporters just didn’t have enough knowledge of what they were reporting and put the wrong spin on it.
The central claim is that CDC stopped testing for swine flu hastily and without advance notice to the states:
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.
The ramifications of this finding are important. According to the Center for Disease Control, CDC, and Britain’s National Health Service, once you have H1N1 flu, you’re immune from future outbreaks of the same virus. Those who think they’ve had H1N1 flu — but haven’t — might mistakenly presume they’re immune. As a result, they might skip taking a vaccine that could help them, and expose themselves to others with H1N1 flu under the mistaken belief they won’t catch it. Parents might not keep sick children home from school, mistakenly believing they’ve already had H1N1 flu.
Why the uncertainty about who has and who hasn’t had H1N1 flu?
In late July, the CDC abruptly advised states to stop testing for H1N1 flu, and stopped counting individual cases. The rationale given for the CDC guidance to forego testing and tracking individual cases was: why waste resources testing for H1N1 flu when the government has already confirmed there’s an epidemic? (CBS News)
The implication here is that this was a precipitous and unilateral decision on the part of CDC that took the states by surprise. They support this by quoting unnamed public health “officials” who told CBS they disagreed with it and quoting from an email from the Council for State and Territorial Epidemiologists to its members (CSTE is a non-profit organization used by state epidemiologists to exchange information and advance their interests). The email was from CDC to CSTE members:
“Attached are the Q&As that will be posted on the CDC website tomorrow explaining why CDC is no longer reporting case counts for novel H1N1. CDC would have liked to have run these by you for input but unfortunately there was not enough time before these needed to be posted.”
It is clear that CDC is saying to the state epidemiologists they are sorry they did not run the Q&As about stopping testing by them , not the decision to stop testing. Contrary to this article, I heard throughout this period that the pressure on CDC to stop the testing was coming from the states, not the other way around. It’s no secret that state health departments are hard pressed to keep their heads above water financially and are short staffed all around. Expensive swine flu testing was something they couldn’t afford. The burden to do the testing was on the states, not CDC, but as long as CDC recommended it, states couldn’t easily stop on their own, especially if neighboring states were still testing. The reason for stopping was confusing (and CBS News shows themselves confused) and bound to be controversial. In effect, CDC decided to take the bullet for state health departments. And CBS News obligingly pulled the trigger.
The kind of testing asked for here — determining the subtype of an influenza isolate — is not a piece of cake. It requires specialized equipment and specialized expertise. Both the equipment and expertise exist in state health departments thanks to money and training CDC did in anticipation of a bird flu pandemic, but it wasn’t designed for high throughput. There was no way states could handle tens of thousands of specimens. If taxpayers don’t want to pay taxes, they shouldn’t complain when the infrastructure isn’t there, but in fact they might legitimately have complained about a laboratory capacity that goes unused except during an influenza pandemic. Since pandemics are unpredictable, that capacity would mostly lie fallow.
As an epidemiologist would I like to have more detailed information about the distribution and pattern of this disease? Of course. Influenza is an important public health problem. Yet influenza outbreaks happen seasonally and we never test and report to CDC individual cases with an eye to having a complete count. Why is that? First, a little digression on how diseases get their names.
A disease can get its name in two distinct ways, sometimes referred to as manifestationally and causally. Manifestationally named diseases are named by how they appear or manifest themselves. An example is cancer. We call diseases with malignant cells that form tumors and grow where they shouldn’t grow, cancers: in other words, by how they look or manifest themselves. Another example is a fracture, a break in the continuity of the bone. Another is congestive heart failure. What caused the disease isn’t in the picture. But the cause of a disease can be the basis for naming a disease, too. Some examples are asbestosis (scarring of the lungs from breathing asbestos), cholera (a disease caused by a specific micro-organism, Vibrio cholerae) or cyanide poisoning.
What about influenza? It’s a weird hybrid. On the one hand it’s part of a group of influenza-like illnesses (ILI), which is a manifestational name. When a doctor tells you that you “have the flu” these days, most often he or she is using the manifestational name. But there is also a causal name for influenza, referring specifically to the ILI caused by infection with influenza virus. That’s the name that can be placed on your disease after some very specific and sophisticated testing to see what is causing your ILI. There are a lot of viruses that can cause ILI (we’ve talked about some of them here a couple of times, for example, here and here), and undoubtedly they are responsible for some ILIs that are now being diagnosed as swine flu. We know, however, that during flu outbreaks, the proportion of ILI that is influenza goes way up, so that the kind of clinical (manifestation only) diagnoses are much more often correct (there is a theorem in probability theory that explains why that is). So it makes a difference that CBS News was looking at data from May, June and July rather than now. At that time there were other viruses around besides swine flu, and the tests indicate that. Why not do better testing?
There are “rapid flu tests” that are done in doctor’s office that can show if you have influenza, but they miss somewhere around half the cases of real flu, so a negative test isn’t helpful, nor does the test tell what kind of flu it is (seasonal or swine flu). For that you need the expensive lab test. And even if we could do all those lab tests, it would entail many days’ wait, during which you aren’t being treated with antivirals, or if you are, then getting the test didn’t make a difference. Most people who have the flu probably never see anyone about it. They suffer and get over it or if it is not so bad they keep going about their business. So they would never get counted anywhere. And many people have ILIs that aren’t flu. And they aren’t counted either as other respiratory diseases.
CBS’s own investigation found that in all 50 states, prior to stopping testing in July, lab-confirmed cases showed that most specimens were not influenza. As I noted, since other viruses cause ILI during non-flu season this isn’t too surprising. What was surprising was the amount of influenza there was at a time when we expect to see very little. Now that flu season is here, the chances that an ILI is truly influenza (causally defined) is much greater. And frankly, there is no possibility of testing all ILI cases for swine flu. There will be millions of cases of ILI and they can’t all be tested and most won’t even be seen by anyone. Moreover, during the period of the CBS “study” many people were having specimens taken that would not ordinarily have seen a doctor. The data they looked at were from all 50 states (and we don’t know what data it was or what they counted or whether they even calculated things correctly) and were mostly cases that were not epidemiologically linked.
This last is important. CBS News cites an outbreak of 250 cases at Georgetown University as an example where no testing was done so it isn’t certain this was a flu outbreak. Admittedly, it could have been adenovirus or respiratory syncytial virus or a bunch of other things. But when something like this happens in the setting of a pandemic, the odds are that it was influenza. More importantly, data on the number of positive specimens for all the people of Georgia over a several month period three months prior is not the same as 250 cases among students who were in contact with each other and that occurred over a few weeks. And think about the alternative? Nothing prevented Georgetown University from testing all those cases. Nothing except that it would have been infeasible and the resources weren’t available, that’s all. And it wouldn’t have changed how they were treated, except perhaps to delay treatment.
Still, as an epidemiologist, we need to know what virus subtypes are out there and roughly where they are. CDC has a multipart surveillance system we’ve written about quite a lot here. It supplies a great deal of useful information for epidemiological purposes and special studies fill in some of the gaps. So it isn’t true that lack of routine testing makes it impossible to know where flu is occurring, what is happening over time and what kind of influenza it is. We have a jury-rigged but fairly efficient influenza surveillance system that has been operating for years and continues to operate.
But compared to countries that have universal health care with efficient electronic medical records we have a much harder time. Our health care system, which is mainly private, isn’t set up to make it easy to get the kind of information people think we should have.
That’s not CDC’s fault. And I haven’t seen that CBS News has done such a bang up job of reporting on health insurance reform. Unless being a stenographer for talking points from the insurance and health care industries counts.
October 22, 2009
October 22, 2009
October 22, 2009
October 22, 2009
October 22, 2009
October 22, 2009
October 22, 2009
October 23, 2009
October 23, 2009
October 24, 2009
October 24, 2009
October 25, 2009
October 30, 2009
November 2, 2009
November 3, 2009
November 22, 2009
November 25, 2009