Why CDC says this year's flu season is "very sobering"

Monday morning, start of week three of the official flu season (which began October 4). CDC's scientific spokeswoman on the flu, Dr. Anne Schuchat has said we are seeing "unprecedented" flu activity for this time of year, including an unusual toll in the pediatric age group. What does "unprecedented" mean? It's not very specific on what precedents are included, but if we confine ourselves to the three years before this one, we can get a good idea of just how unusual this flu season is. This week CDC unveiled a new graphic for their Emerging Infections Program (EIP) (I liked the old one better; this one is not very legible), the component of the surveillance system that tracks laboratory-confirmed influenza-associated hospitalizations in children and adults. It collects data in 60 counties covering 12 metropolitan areas of 10 states (San Francisco CA, Denver CO, New Haven CT, Atlanta GA, Baltimore MD, Minneapolis/St. Paul MN, Albuquerque NM, Las Cruces, NM, Albany NY, Rochester NY, Portland OR, and Nashville TN). It appears CDC has added six new sites (in IA, ID, MI, ND, OK and SD), but the data here are for the original 10 so comparisons can be made. This is a passive surveillance system that reviews hospital laboratory, admissions and infection logs at sites chosen to allow calculation of rates per population in the hospital catchment areas. Here is what the graphic looks like as of last Friday:


CDC Source, full size here; legible on the .pdf version (page 8) (hat tip OmegaMom)

Weeks are on the horizontal axis. There are five age group panels (0 - 4 years at the top, seniors at the bottom) and at the right side of each panel you will see lines gradually ascending from week 40 (October) to week 20 (April), CDC's traditional flu season. Everything to left of week 40 in each panel is prior to or just after the official flu season and is essentially zero for the three prior seasons, i.e., during the "off months" we don't see lab confirmed hospitalizations for flu (the prior seasons are color coded but I can hardly read the legend and the fact that I'm color blind doesn't help). The reason the levels are close to zero out of flu season might be because we haven't been looking very hard. After all this system depends on someone doing a test for flu on hospitalized patients and if they don't believe there is any flu during the summer, the test doesn't get done. But it is almost certainly true that whatever flu is around at those times of year, it is much less than during the usual non-pandemic flu season.

As the season progresses you will see that the cumulative number of people who were infected with flu per the populations in each of the age groups served by these hospitals rises. Think of this rate as reflecting the chance that someone in that age group will get infected with flu and be sick enough to wind up in one of the EIP site hospitals with his/her case confirmed by a lab test. Some years are worse than others and you can see that the rates of infected persons per 10,000 population ends up at different points by the end of the flu season in the spring (week 20) during the three different years (population rates, left vertical axis; case counts on right axis). Flu is like that. Not every year is the same. It depends on what the predominant seasonal flu types and subtypes are that year and probably lots of other things we don't know.

The "unprecendented" year we are having shows up in the left of each panel. The rates are a solid line running across the bars. the bars are case counts (note to CDC: lose the bars. They are obscuring the picture). To see how unusual this is, look at the top panel (0 - 4 years), where the solid line has risen to 1.4 cases per 10,000 infants and toddlers in week 40 (first week in October). In the three previous years that seasonal risk level isn't reached until the 3rd week in January. We are 3 months in advance of the last three years by this measure, and the case count for that age group is still rising. For the 5 - 17 year old panel the difference is more dramatic. We've already reached the risk level we would normally see for the whole flu season, and we are just getting started. That's the group being hit the hardest, and half the fatalities since September 1 have been in the 12 - 17 year old age group, confirming that.

For adults between 18 and 50, the picture is like that for the under 4 year olds: about 3 months in advance compared to the bad flu year of 2007 - 2008 and already exceeding that for the entire flu seasons of the other two years. This is the age group populating the ICU beds. Even though population rates may be smaller, there are many more of them.

When you look at the 50 - 64 year old age group you start to see a different kind of difference. The bad flu year of 2007 - 2008 is now clearly visible and the main targets were the over 50, and even more striking the 65+ age groups. That's typical of a bad flu season during usual times. You can see that the 50 - 64 is still being hit, well in advance of usual, but the 65+ age group looks more like the usual seasonal year, although even here we are in advance by months. But so far this year the swine flu hammer has fallen elsewhere and it is this change in the epidemiology -- the pattern of influenza in the population -- that is signaling the presence of a pandemic strain.

It is true that seasonal influenza kills a lot of people every year. They are mainly seniors, people like me. People care about seniors, of course, but our deaths are considered part of the natural order of things. Old people die. If it's not one thing, it's another. And of course our mortality rate is very high, compared to all other age groups. Even if the number of infants, children, teens and healthy adults double or triple or quadruple, the number of deaths may not ever reach what happens normally to seniors during seasonal flu, but the psychological and social impact is considerably greater. That's one of the fallacies in comparing the numbers of deaths from this flu with the usual seasonal flu.

Where this is going to go, we don't know. But as CDC's Dr. Schuchat remarked concerning the increased mortality in babies, children and teens, what we are seeing is "very sobering." That's not because of the numbers of deaths, but because of who is dying. And as a parent and grandparent, I have to agree. Those deaths are very sobering.

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Would it be worthwhile to consider reporting it as estimated years of life lost to put it in more meaningful context. Same number of deaths but most with 40 to 80 more years expected on average, as opposed to an average of maybe 5 to 10 most years (making it up) would translate to this years influenza resulting in 8 to 40X more years of life lost.

Uh 4 to 40X, but you get the point. Fill in with real numbers.

How many deaths in the age groups that one would normally expect to experience it (teens and young adults) have been attributed to cytokine storm?

By Katharine (not verified) on 19 Oct 2009 #permalink

There was a recent computer model (and darn it, I can't seem to find the link this morning) that predicted this first wave would peak at Halloween, with 8 percent of people catching it that week alone.

This model seemed to suggest a short-lived wave that peaks and then drops quickly. Yet, if you look at the charts for states like California, they don't so much as have a wave as a burn -- a smaller peak that never drops. Is there speculation on what might happen this fall? Or is that model just an educated guess?

Finally, in regards to your prior post: 2/3 of those infected will really never, then, realize they had the flu? I think that's really interesting in an outbreak like this one when so many people are being infected. There are tons of people walking around with "bronchitis" right now or colds with no fever or fatigue that quickly develop a bronchial cough. My own family just recovered from this: A week or so of UR symptoms and productive cough, but never bedridden and no fever. Any other season I would call these infections colds, but now I wonder.

If you--or other folks like you with a little more "oomph" than us everyday non-epidemiology folk--could get the CDC to produce that damned chart in a more legible format, it would be most helpful. Even when you see it in "full size" it's practically illegible, and it's information that I think people *should* be seeing.

omegamom: Yes, it's an atrocious graphic. CDC folks read this blog but don't reply to bloggers.

Very sobering graphs... after you actually realize what they mean. This is not your ordinary flu.

By Cosmoskitten (not verified) on 19 Oct 2009 #permalink

I dunno, maybe because I'm a senior, maybe because I've been with the Gray Panthers (off and on, admittedly) since 1975, but I can't help but find ideas like "People care about seniors, of course, but our deaths are considered part of the natural order of things" (or forms like "estimated years of life lost") rather agist--or, if that term sounds too moralistic, then let's say: some mix of (1) valuing less (the lives of) one portion of the population and (2) denying (by treating as "oh it's just natural, who could mind it?") the natural fear of death (even through old age). I realize this is a bit off-topic, but it unfortunately may have some serious public health effects.

Revere, in spite of my previous comment, I find your discussion and analysis in this post superb and informative, providing very needed information. Thanks.

Here's a somewhat related question. I just tried to get a (seasonal) flu shot from my primary care physician. They are all out of vaccine, and have no plans to get more. My local pharmacies have cancelled half their planned flu shot clinics for lack of vaccine. Only the local walk-in clinic had any, and they expect to run out this week, instead of months from now.

In other words, on the basis of this very local and fragmentary sample, not only is this a worrisome looking flu season, but there seems to be a serious shortage of seasonal flu vaccine. I have not seen any mention of this shortage in the media or in online discussions, nor in the CDC and others recommendations about vaccination.

Do you know anything about this? Is there a general shortage of vaccine? If so, what happened?


By ecologist (not verified) on 19 Oct 2009 #permalink

Makes me extra-aware of the benefits we've seen due to widespread polio, MMR, etc vaccinations.

We're no longer used to seeing young folk die of infectious causes, when it used to be pretty normal.

By Lisa the GP (not verified) on 19 Oct 2009 #permalink

Paula: You make an interesting point. I'm not sure what to think. Since I am in that age group and have two sibs close to 80 and friends and contemporaries in the same age group and I myself am still actively working and doing science and my mother was still an active professional into her 80s I am not "writing us off." But I was trying to express a view Ithink quite prevalent, one which infects me, too, and one which I think explains why numbers are not the only thing involved here.

betty: The moview illustrate a different issue, but what is most puzzling is that CDC had a decent graphic for this up until now. Why they switched to this new version and made it so low resolution, I have no idea. I hope they fix it.

ecologist: The whole flu production apparatus was under such stress and uncertainty I wouldn't be surprised if things are messed up and real shortages happen, especially as there is increased demand. But I have no inside info on what is really happening.

Lisa: Excellent point. Wished I had thought of it for the post.

omegamom: Thanks! I'll update the post. They must have some kind of scanned low res version on the website.

Thanks, Revere. I think we agree that that prevalent view infects us all and that there is more than just numbers involved.

"This is a passive surveillance system that reviews hospital laboratory, admissions and infection logs at sites chosen to allow calculation of rates per population in the hospital catchment areas."

Isn't that active surveillance?

"The principal functions of EIPs are to perform active, population-based surveillance for infectious diseases..."

chirpie: I described it as passive surveillance because it collects data not designed for surveillance. CDC has several categories of surveillance and they often call systems where you call the facility "active" surveillance. I don't use the term that way unless the system is designed to collect that information. I discussed this with some surveillance experts and they could not agree on a definition. I described it explicitly enough so that you don't have to know what it's called to understand what was done.

I guess that is why is called an antigenic shift: nothing else but strains similar to the pandemic strain is circulating. I was appalled by hearing the recommendations for almost everyone to get the seasonal influenza vaccine. I am not sure about the grounds for such recommendation, though it was convenient and some may not want all those batches to go waste. But there is something even worse: recommending washing your hands. Since when the influenzavirus is transmitted like the common coldviruses, and the like -SARS included? Is because soap is available? I think public health losses more credibility by hanging on to half truths, and telling half lies.

I am an American living in Tokyo. My healthcare is covered by Japan's national health insurance system (hooray).
According to the Oct. 20 Japan Times newspaper (http://search.japantimes.co.jp/cgi-bin/nn20091020a1.html), Japan has the following swine flu vaccination schedule:
"Swine flu vaccinations began Monday with doctors and other medical professionals given priority because supplies are limited.
About 1 million medical workers are to be given the domestically produced vaccine first, according to the health ministry's priority ranking.
Next will be pregnant women and people with specific chronic diseases, beginning in November, in line with the government's plan to combat the fast-spreading H1N1 flu virus.
Children between the ages of 1 and 8 will be vaccinated starting in December, and parents of infants early next year."
Question: Does this schedule seem slow compared to what's planned for the US and European countries? If yes, why would Japan be slower than other advanced countries?
I am the parent of an infant. Apparently, I have to wait about 3 months for my turn. How about such parents in the US?

Like in any study we only have part of the picture. If we extrapolate early results (cases) into the future we will have a very bad outcome. But lets hope that the cases peak early, then taper off. That would be best case scenerio given current data.

Victor: We discussed the (good) reasons for getting both vaccines here. Whether or not handwashing is good for flu is an open question, but it is demonstrably a good idea for many other respiratory intestinal viruses.

John: The order of priorities is about the same as the US. The actual implementation, including when the vaccine will be available to each group, is heavily dependent on the supply chain in each country, so it is hard to compare.

JD: I agree with you. With flu, predictions are hazardous. But so far it doesn't look good.

"That's one of the fallacies in comparing the numbers of deaths from this flu with the usual seasonal flu."

Sure, absolutely. But one of the fallacies in comparing doctors' visits or even hospitalizations is that if people are more worried about H1N1 than a normal seasonal flu, thanks to all the warnings, then they'll go to the doctor about flus that perhaps they would have just stayed home with in other years. More flus are likely to be cultured and verified by laboratory as well.

Death statistics have the one advantage that deaths are almost always reported and tallied. The doctors' visits numbers are the least comparable between years.

By John Thacker (not verified) on 20 Oct 2009 #permalink

John: You are correct, although there is little doubt that what these data are reflecting is real. If you look at the P&I mortality data you will also see it poke above baseline plus 1 SD (the threshold) now, which also hasn't happened at this time of year in the previous seasons, so it is consistent. The problem with mortality is that it is imperfect because we don't know cause of death from influenza, only some vague measure of "excess mortality," so while it is comparable year to year we don't know exactly what we are comparing.

John Re; Vaccination schedules,
Actually, here in the Metro DC area, most health care providers have already been vaccinated and the kids are getting it now (6 months-18 years). Some area counties started vaccinating kids 2 weeks ago. Anecdotal, but I have friends in Miami and Phoenix whose kids have been vaccinated at county clinics. Seems like waiting till December, especially when it takes 2 doses at least 3 weeks apart for smaller kids to have good immunization, is a tad late. Maybe the season is different there? Good luck.


The reason the stuff you are mentioning sounds "age-ist" (or whatever term you want to use) is that LIFE is "age-ist". As he mentioned in the original post, "Old people die." This is simply the way the world works. (Ever notice how often there's a headline about the oldest person in the world dying? Yeah, it's OFTEN.)

This is the way it has always been, and, barring divine intervention or amazing medical progress, this is the way it will be for the foreseeable future.

This is not to say that we don't CARE if old people die, or that old people should simply be written off. It is simply acknowledging and preparing for the hard fact of life that old people are MUCH more likely to die.

Also, as one of the commenters mentioned, there is the issue of "expected years of life lost". When my great-grandmother died at 92, I was sad because I was going to miss her, but not because I felt she had missed anything - she had lived a long, full life, longer and fuller than most. To EXPECT more than that is setting yourself up for disappointment (though people can always HOPE, of course).

When a friend of mine died the night before I graduated high-school, it was much, MUCH more shocking, though it was less meaningful to me personally. What happened to all those years of expected life?!?

This is the difference being discussed. These realities do indeed lead SOME people value the old less and consider them "expendable" for budgetary or political reasons (ideas which need to be resisted very strongly), but that doesn't change those underlying realities.

Umm, what the heck is "progressive public health"? Old people stealing even more money from their grandchildren? Government running the health care industry with the efficiency of the DMV?

Right. All the statistics are unfortunately more imperfect than we'd like.

There's more hype and awareness this year. That can mean that people take more precautions, which is good, but can make the strain look less virulent in the numbers than it really is. Perhaps if people took normal precautions instead of extra precautions, things would be much worse.

It's certainly the case that people are going to doctor's offices and requesting lab tests when they have influenza or symptoms that they would have just stayed home for a few days in other years. Ask anyone who works in a doctor's clinic about that.

Deaths are indeed above the baseline plus one standard deviation in the latest week. OTOH, just three weeks ago they were more than a standard deviation below the baseline. One week is rather thin data. Deaths were many standard deviations above the baseline for several months in the Winter 2007-08 flu season, but that didn't get nearly as much attention as either avian flu in 2003-05 or the current swine flu.

Another problem with death is that it is, as you say, "pneumonia and influenza," which means that in some years (this one or previously) the deaths can be from pneumonia from other causes that is never laboratory-confirmed as flu. That could argue that this is either more or less serious than in previous years; probably more, since elderly deaths from pneumonia are probably more likely to be from non-influenza causes than among young people.

As the BMJ notes (http://www.bmj.com/cgi/content/full/339/sep03_2/b3471) a large percentage of the elderly have cross reactive antibodies to novel H1N1. That may mean that this is a virulent strain, but it's similar enough to pandemics of decades past that the worst affected are the young, who don't have previous exposure.

I do think that this is serious, but people in general often mistake what statistics actually say. Under-reporting and over-reporting in different years make epidemiology much more difficult (as in any statistics.)

By John Thacker (not verified) on 20 Oct 2009 #permalink

The other question we don't know concerns the flu season. It's indisputable that novel H1N1 has started out of season. The question is whether that means that it will also decline ahead of schedule, or whether that only presages being much worse once the traditional flu season starts.

Google Flu Trends for New Zealand (http://www.google.org/flutrends/intl/en_us/nz/) suggest the former, thankfully. Flu peaked in New Zealand two months earlier than normal, but August and September flu rates were significantly below last year.

If novel H1N1 means an earlier, but not too much worse, flu season, that's tremendously better than the other hypothesis.

By John Thacker (not verified) on 20 Oct 2009 #permalink

John: Umm, what the heck is "progressive public health"? Old people stealing even more money from their grandchildren? Government running the health care industry with the efficiency of the DMV?

It's easier to say what it isn't: Free pass for Wall St., Iraq, Afghanistan, climate change denial, or Birther/Deather tin foil hattery, among other things.

All I see right now is a normal flew season starting earlier. Seriously, slide the scale and wala, it's pretty normal.

Is it reasonable to infer from the charts, that the school-age population is affected less than the others, or at least, that the change from previous years is less pronounced in this current year?

If so, does that say that the message about infection (wash, wash, wash your hands, etc) is getting out, to the specific group that we're teaching formally?

By Jeff Bowles (not verified) on 20 Oct 2009 #permalink

Joe, Jeff: It's hard to make comparisons precise from these charts for reasons John #24 suggests. What is clear is that this is an extremely abnormal flu season. Change in time of year is very abnormal and the population being hit is very abnormal. The second is characteristic of pandemic strains. So "sliding the graphs" is not what is involved here. As we said in an earlier post, it's the epidemiology, not the clinical behavior of the virus.

"Is it reasonable to infer from the charts, that the school-age population is affected less than the others, ..."

It looks to be the opposite: the 5-17 yo cohort has already reached levels this early in the season that exceed the incident totals for all of the prior 3 years.

Interestingly, regions 4 and 7 seemed to have had this flu strike the soonest; by a month or more in some comparisons. I'm not sure about region 7 states (IA,KS,MO, and NE), but the region 4 states commonly start school in early August, whereas in the North East they typically start in September (e.g., in Boston, on Sept 10th).

Perhaps one important factor in the regional differences in the timing of the onset is when schools started back up this fall.

Re the timing of this flu season--we've been comparing it to recent seasonal flu seasons, but have we figures for the '57-'58 Asian flu event? I'd guess a really close parallel there would be the only thing, short of a lowering of current rates, that would be very reasuring.

Deoxy: I'm not sure there's much point to responding--guess my word "agist" hit something (which is why I explicated what I actually meant, which you can check in post 9). But "that's the way life is"--and its more usual form, "life ISN'T fair"--has never been a guide re human behavior; and I presume you don't wish to move to the usual next step, "That's how people are" "It's just human nature," etc. Yes, old people die--and so do cancer patients, heart failure victims, ARDS patients, young people--but some live on, for varying lengths of time; medicine is about preventing deaths. And what I was saying is that social attitudes (like "Oh well, old people die in a few years anyhow") can themselves be a risk factor, as perhaps may possibly be happening re the "swine flu" vaccine.

Some thoughts on the "agism" discussion.
There are distinctions in people's thinking before and after events, as well as regarding a known individual or the collective population.

Regarding the collective population, I don't sense any "before the fact" thinking in the direction of "we won't vaccinate the old folks, they're gonna die soon anyway". I do see some thinking after the fact, noting that "OMG, 2 children have died; (or 15 or 43)" and a reaction that we need to get them vaccinated because it's unusual to see large numbers of children die from the flu. In normal flu seasons enough older people die that there is a big push to get them vaccinated, and kids are pretty much ignored. And looking at the population these are logical conclusions - usually more older people get very sick and die from the flu. Right now an unusual number of younger people are, so that's where the focus is.

As for specific individuals, I'm sure that if a 90 year old grandmother dies of the flu right now her family will be distressed, and perhaps even angry that there wasn't a vaccine for her in time to possibly save her. I'm mighty close to that age group that is lowest priority right now, and I understand why that's so; however I'm fond of my individual life and heartily hope that they get enough vaccine out there that "my turn" comes sooner than later; and comes before the flu bug hits me.

By Catte Nappe (not verified) on 20 Oct 2009 #permalink

Good points, Catte Nappe. I agree that the the unusual (and pandemic) nature of the distribution is very much part of the thinking and rhetoric re who's getting this flu. Yet I wonder if some of the concern that this flu is hitting persons who may not be old, not disabled, not "with underlying conditions" (and that it struck hard first in North America, not people "down there somewhere") doesn't come from the sort of us-and-them distinctions by which it's "serious" when it's "us" getting hit. But perhaps this is careless theory.

Not sure where to put this, but since we're doing age distribution etc. here-- I saw this while glancing at Reuter's a little while ago, and am not sure how to regard either the study or the (intuitively sensible) potential that this Lieberman brings up. "Dr. Jay Lieberman, medical director for Quest Diagnostics and a pediatrician at the University of California, Irvine, says data from Quest's testing, based on 76,500 specimens taken between May 11 and October 11, 2009, can supplement the CDC's findings, which cover fewer than 5,000 patients. . .The sharp rise in cases in children came at the end of August and beginning of September, Lieberman told Reuters. . ."What is interesting is that we are now seeing delayed by several weeks a rise in other age groups--in the elderly, in people aged 50 to 64 and in children under 5 years of age," Lieberman said. . ."What we have seen in the pandemic so far is that the elderly have been relatively spared. That may start to change . . ." Reuters also carried bits of the other Lieberman (Joe)'s comments at a Senate hearing, with the senator quoting a (CDC?) estimate of possibly 150,000 to 300,000 Americans needing intensive care beds as a result of this flu. Has anyone heard that figure?

Well here's some sobering numbers ...

Texas is several weeks ahead of the rest of us when it comes to H1N1. What is happening there may give the rest of us a heads up. Their current totals http://www.dshs.state.tx.us/idcu/disease/influenza/surveillance/2010/

92 ICU admits, 82 deaths with confirmed H1N1 from 9/20 to 10/10. Now that does not mean that of 92 ICU admits 82 died - some of those deaths never made it so far as the ICU, but still, that ratio made me do a quick inhale.

They are also up to 2% of H1N1 being Tamiflu resistant.

Almost 13% of all visits to sentinel clinics are ILI related and of those 30% of them were in kids 0-4. 85% of those ILI related visits were in those under 24.

Also, (via a link to pdfs) in week 40 there were 14 ICU admits for the 18 and under group. In the period 9/20 to 10/10 there were 28 PICU admits (out of those 92 total ICU admits) Mind you I am not happy about 14 ICU admits in a week, but it so far it doesn't seem like a number that will overwhelm their PICU system.

OTOH, it doesn't seem like they are too close to peaking yet ...

Sobering? Maybe not. I think I need a drink!

Paula - that number came from the Report to the President…

"By the end of 2009, 60 to 120 million Americans would have experienced symptomatic infection with 2009-H1N1; nearly 1 to 2 million would have been hospitalized, with about 150,000-300,000 cared for in ICUs; and somewhere between 30,000 and 90,000 people would have died, the majority of them under 50 years of age.
We emphasize that this is a plausible scenario, not a prediction. By way of comparison, it is less severe by a factor of three (in terms of expected deaths per capita) than the âreasonable worst caseâ planning assumptions, publicized by the UK government, for the H1N1 resurgence in that country. "

To emphasize what they said - not a prediction, a "plausible scenario".

Don S.--thank you. Not sure why I didn't realize that. OTOH, those Texas figures you just posted are. . .maybe we better break out a great many drinks. Especially with the latest vaccine delay announcements. And here in Oregon, the antivirals situation may be termed sparse---though the 2percent Tamiflu resistance in the Texas figures may make this less relevant. Maybe it's time to kick back and watch "Threads" or "Day After" again.