Normal Flu
If I were to say that this year 30,000 Americans would die from the flu, you’d probably think I was offering an alarmist take on the current swine flu outbreak. In fact, I would be offering an extremely optimistic take on influenza in 2009. According to the Centers for Disease Control, the country sees about 36,000 flu-related deaths in a normal year and around 200,000 hospitalizations. It’s standard for between five and twenty percent of the population to contract the flu in any given year.
Given all that, not only do we face the risk of an unusually bad pandemic of “swine flu” we also face a risk of panic. Apparently, very high levels of flu-related hospitalizations and deaths are actually pretty normal. But the media doesn’t normally cover them as national news stories. The heightened awareness of swine flu risks, however, means that anything flu-related is going to get dramatically inflated attention.
70 Responses to “Normal Flu”
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April 30th, 2009 at 8:27 am
First?
First!
April 30th, 2009 at 8:30 am
If I get the flu, how will I know that it’s swine flu, so I can get people to panic with me without feeling alarmist?
April 30th, 2009 at 8:30 am
Matt – are you suggesting this is just media hype? It seems to me that serious health organizations, like the WHO, are ringing loud alarm bells about the swine flu. I don’t remember hearing the same kinds of comments during previous flu scares. The interesting question is – what is different about the swine flu that is worrying world health experts?
April 30th, 2009 at 8:35 am
http://www.huffingtonpost.com/2009/04/30/biden-swine-flu-made-me-t_n_193473.html
April 30th, 2009 at 8:35 am
Right, but there’s not much else they can do. They’re concerned that it has the possibility of killing 30M, not 30K.
Personally, I’m watching for the ages and conditions of the people who are dying. If they’re young, old, or otherwise immune compromised, it’s pretty much the same as “normal flu.” When healthy 20-years start dying, I’ll get worried.
April 30th, 2009 at 8:38 am
The flip side of this is to say that flu is a serious public health problem, every year, and that unsexy control measures such as vaccination, hand washing, and paid sick leave should get more attention on an ongoing basis.
April 30th, 2009 at 8:38 am
mr. bispo — that sounds like another Biden screw-up. If people en mass were to stay out of schools and off planes and subways at this point, it would be a huge overreaction. No other official has said something so stupid. If you’re sick, yes, stay away. But not if you’re well.
April 30th, 2009 at 8:41 am
As I understand it, what is different about a flu pandemic is that otherwise healthy people with strong immune systems die of the disease. It is not surprising to health care workers or the public that the very old, very young, individuals with lung or heart conditions would succumb to the seasonal flu. However, during a pandemic, where a completely new strain develops, it is the healthiest individuals, between the ages of 15-35, with strong immune systems who experience the highest level of deaths due to the outbreak.
April 30th, 2009 at 8:43 am
7: Really it depends on the situation. If you are looking at the flu epidemic of 1918/1919, that is actually the correct advice. We do rely on public health officials to give guidance that balance the cost of disruption to daily life against the threat of massive death. Biden, or any politician really, is not the kind of person to be offering this guidance, though.
April 30th, 2009 at 8:44 am
8: Certain types of flu can cause that kind of reaction, but I haven’t seen any reporting/evidence that it’s a concern yet for swine flu. It’s also not the definition of a pandemic afaik.
April 30th, 2009 at 8:49 am
Even if nobody dies from the swine flu, imagine if 200,000 people get seriously sick all at once, instead of over a year’s time. Even a mild pandemic would stomp all over the green shoots of an economic recovery (if they exist, which I doubt).
April 30th, 2009 at 8:57 am
The excessive media attention is an inescapable, and in the long run small, price to pay for being well-prepared just in case worst comes to worst.
A pandemic is just a very widespread epidemic. If we’re lucky it will be a pandemic of more or less “normal” flue, but many people don’t realize that there’s still a very significant mortality rate associated with that.
April 30th, 2009 at 9:00 am
While there is certainly some cause for worry as with any unknown at this point and the WHO and the government certainly need to think worst case scenario and plan, the media coverage is just crazy. There are less confirmed cases in the entire U.S. than I personally know people who had the “regular” flu this year. But if I watched the television news for more than a hour a day, I would not leave my house. They are treating it like we’re in the grips of the plague at this point. Yes, it could get worse and everyone needs to take normal, keep yourself healthy precautions for now, but it’s not yet time to lock yourself in your house. There has to be a way that they can inform properly without scaring everyone to an extreme.
I went out to walk my dog this morning, and mother walking her elementary school-aged kids to work saying, “no, you do not have the Swine Flu.” Then she said to me, “my kids need to stop watching the news…”
April 30th, 2009 at 9:05 am
Today you will be reading that this strain of flu presents rather mild symptoms. This is great news and I think it is confirmed. So why the panic? Tens of thousands will likely die in the US because of it. Not so many but if one is your baby how will you feel?
Right. You would spend the rest of your life thinking what ifs? All the precautions possible to limit the spread of the flu will save hundreds if not thousands of people agonizing over what ifs.
April 30th, 2009 at 9:06 am
This is similar to the anthrax scares, post 9/11. Because some samples had been mailed and some people infected, nearly every respitory infection, for a long time after, was tested for anthrax. Some positives, apparently unrelated to the mailings, were seen. It was never published, afaict, if these positives were false or ‘normal’ (part of a background of seldom deduced but nonetheless present infections. An interesting question to which I’d like to see the answer..)
But we know that ‘ordinary’ influenza happens, and ought to continue to happen, even in the middle of a pandemic of extraordinary strain.
It’s arguable that the number of deaths and/or hospitalizations are “very high” relative to the population over that time period. There are some strains of influenza that travel relatively lazily through the population and take their toll, especially on the aged and the infirm, during a given period time (here about a year). Virulence, the new variable in the H1N1 strain on the edge of pandemic, is what’s got the WHO worried. In addition, the 1918 pandemic, which involved a variant of H1N1, was unusual for a very scary reason: a disproportionate amount of ‘young and healthy’ persons, who might otherwise be expected to cope well with influenza were actually the larger portion of it’s victims. The present theory as the particular variant of H1N1 seen in 1918 was able to trigger a severe ‘overreaction’ of the immune system, so, paradoxically, the stronger the immune system the stronger the ‘overreaction’ and the higher the likelihood of severe illness. This is only a theory as we don’t have much information from that time period.
Panic is often a component of misinformation. Complacency, too, can often be the byproduct of misinformation. So the enemy, here, is misinformation.
April 30th, 2009 at 9:07 am
Well, it’s not like we have swine flu instead of a normal flu outbreak. The regular flu season is just ending; this would be 30,000 additional deaths. If it’s a mild pandemic, which it may well not be.
Not that that’s a reason for panic – but it does seem to warrant a fair amount of extra media coverage.
April 30th, 2009 at 9:11 am
There are no human vaccines for this strain of swine flu. There is no industry dedicated to making new swine flu vaccines every year or so like there is for regular flu. There are only two anti-virals that work against it. Since flu viruses frequently change, there is a chance they will stop working. The existance of multiple, significantly different flu strains that can infect humans, presents an increased risk that there will be genetic changes rendering the new strains immune to new vaccines at a rapid pace.
April 30th, 2009 at 9:18 am
@alan:
“and paid sick leave should get more attention on an ongoing basis.”
Amen.
April 30th, 2009 at 9:20 am
#3 and others wondering what’s different about swine flu than regular flu:
Its different and people don’t have immunity(partial or full) to it so we’re wide open for more serious cases than you usually get with seasonal flu that most people are partially protected from.
Normally the seasonal flu varies from year to year in the viruses surface proteins (what your immune system reacts to) by only a little – meaning your body builds on the antibodies it has from previous years. With any new potentially pandemic flu (avian, swine, spanish flu of 1918, etc), the surface proteins are really different – a completely novel arrangment that your body hasn’t seen before and doesn’t have protection for.
That’s the difference between 30,000 deaths a year, and the potential for millions (depending on just how virulent this virus is and on just how different it is from previous viruses). If its mild or if it looks anything like other H1N1 viruses that parts of the population are immune to it will be a mild pandemic. If the opposite, it’ll be 1918 and we’re looking at deaths in the millions.
April 30th, 2009 at 9:21 am
“what is different about the swine flu that is worrying world health experts?”
In addition to what Njorl said, some of the early reports out of Mexico indicated that young, otherwise healthy people were dying from this strain of swine flu. Typically, the overwhelming majority of flu deaths are people who were already very old or ill. In the Spanish flu pandemic of 1918-1919, the majority of fatalities were young adults. So this was seen as an early warning sign of an unusually deadly outbreak.
April 30th, 2009 at 9:22 am
Um, no. An epidemic, as it is ‘traditionally’ thougt of, is confined to a single species (usually humans) and, it is thought, that the mutations seen, however, are limited to the mutations possible within that single species. It’s unclear if some past epidemics might have been subsets of a pandemic. Our understanding of science, medicine and epidemiology were relatively poor for all but the last 50 years.
A pandemic, however, is a disease that can jump from species to species and can mutate in unknown and surprising ways as genes from different specie mingle and mutate. So, by it’s very definition a pandemic can never be just a bigger outbreak of “normal [influenza]“. That’s why the CDC and WHO are being cautious and pro-active: we’re in a blind spot and it’s not clear what the influenza will turn out to be. Right now, it could be as likely to be a big nothing as a big something… It’s nearly impossible to tell.
In general, I’m pleased with the efforts of the CDC and WHO and think they are being extraordinarily responsible and responsive. I think we’re on top of it. But, as I’ve taken pains to point out with your comment, and other comments, there continues to be a tendency towards miscommunications and misinformation. That, more than anything, can engender panic so we ought to be careful.
April 30th, 2009 at 9:33 am
Apparently, very high levels of flu-related hospitalizations and deaths are actually pretty normal.
Deaths by influenza account for less than 2% of deaths in the U.S.. Begin panicky, flu-derived special pleading for government control of another 10% of GDP (single-payer health care) n…………….ow.
April 30th, 2009 at 9:34 am
There seems to be a localized, non-flu contributing factor to the swine flu deaths in Mexico. This flu may not even be as communicable as ordinary flu. (Of course, I may be speaking from my genius for emphasizing the wrong thing and in a week 10% of the Western Hemisphere may be dead.)
April 30th, 2009 at 9:40 am
Yes, because the only possible benefit of single payer healthcare is to combat the flu.
April 30th, 2009 at 9:48 am
There are still a lot of questions about the circumstances in Mexico. I heard on NPR, that the poorer areas where there have been some flu cases have a critical water shortage. People are not washing their hands (or anything). It might be that it won’t be able to spread significantly in areas where good hygiene can be practised. It’s not worth gambling on, but it’s worth hoping for.
April 30th, 2009 at 9:53 am
Petr, you have no idea what you’re talking about wrt the definition of “pandemic’.
http://www.medterms.com/script/main/art.asp?articlekey=4751
(By the way ALL flu, like virtually ALL human epidemic diseases, originated in other species. http://www.nature.com/nature/journal/v447/n7142/full/nature05775.html)
April 30th, 2009 at 9:57 am
Ya well my hospital in Phoenix has its whole E.R. on droplet precautions and everyone who thinks they have the swine flu is segregated to one side of the room. Yesterday there were a couple hundred, out of whom six had ordinary flu.
We’re beyond full, and diverting ambulances at least part of every day. I think our biggest fear in the hospital is how many employees are going to call in sick if the schools start closing and they can’t get last minute daycare.
April 30th, 2009 at 10:13 am
Re jeffery davis at 23: “There seems to be a localized, non-flu contributing factor to the swine flu deaths in Mexico. ”
———–
I would be curious to know how many deaths occurred within the ethnic Indian group. The emigration out of Africa across Eurasia and down the Bering Strait resulted in Latin American Indians having only a subset of the full human set of genes –due to the filtering effect of a much smaller gene pool.
Plus, as Jared Diamond noted, American Indians experienced massive dieoffs from European diseases (smallpox,etc) because they have not been sleeping with livestock for 4000 years the way those with European ancestry have.
April 30th, 2009 at 10:26 am
You found a link that confirms your view. Very well. Are you comforted now?
Epi – upon (or within) demos people (or geography.
Pan – across (or throughout) demos people (or geography).
Your demos (people) centric view is part of the issue.
Another link. You must be very comforted. How is that different than what I said about the possibility of past epidemics being subsets of (undetected) pandemics?
But a pandemic is NOT simply an UBER-epidemic. If it were, every seasonal influenza would have the very real possibility of becoming a pandemic… and, therefore, we’d have seen many many many more pandemics (like… several… every year) over the course of the last few thousand years.
If the link betweem epidemic and pandemic were as bright and as straight-lined as you like to believe, we wouldbn’t be around to have this conversation.
Duh.
April 30th, 2009 at 10:28 am
This is not the normal flu though. Many thousands of people also die in car accidents every year, but if we’d just found out about some new phenomena that could cause thousands or millions more car crashes, we wouldn’t just say “meh, we’ve already got car crashes, who cares about more?”
We will still have all those hospitalizations and deaths due to normal flu. This is a new disease. If the name of the disease didn’t end in “flu”, would you still be making this argument? It doesn’t seem much comfort to the many additional people who are likely to die this year that their deaths will could be considered to be added to a baseline of deaths for a similar virus
April 30th, 2009 at 10:32 am
petr, duh indeed. Carry on babbling senselessly, if you like. I have better things to do than educate you.
April 30th, 2009 at 10:36 am
Petr,
Despite what you say, pandemics don’t necessarily involve species-jumping. The difference between an epidemic and a pandemic would seem to be one of geographical extent — a pandemic is a “global epidemic.”
April 30th, 2009 at 10:38 am
But for those less stupid than petr who would like accurate information, the reason that pandemics don’t happen all the time is simple- they require novel recombinant viruses to which there isn’t an existing reservoir of immunity. That’s the reason why this new swine variant is likely to cause a pandemic, which is an entirely separate issue from whether it will prove to have more serious symptoms than “normal” flu viruses.
April 30th, 2009 at 10:40 am
Apparently, you don’t. Else, you’d be doing them. When I have better things to do, I do them. The thing I’m doing now is attempting to point out the simple in your simpleminded views. If it makes no sense to you, I can’t be held responsible… Duh.
April 30th, 2009 at 10:41 am
And again, ALL flu viruses result from species-jumping, usually from birds but sometimes from pigs (though the current virus also contains some avian sequences). Like most other human epidemic diseases, it’s a relatively recent evolutionary novelty which could not have existed before the agricultural revolution.
April 30th, 2009 at 11:06 am
Like most other human epidemic diseases, it’s a relatively recent evolutionary novelty which could not have existed before the agricultural revolution.
The best choice would be for people to eschew eating animals or their by-products. Animals contain no needed nutrients that plants don’t. Close interactions between humans and animals in their torture pens lead to all of these crossover diseases, and real killers like heart disease and stroke (which far outpace flu) are much reduced in animal-food avoiding humans. Plus, animal foods are much more wasteful than plant food.
April 30th, 2009 at 11:49 am
Steve — It’s probably more correct to say that the current H1N1 has avian (PA, PB1, PB2) and human (PB1) ancestry, but it’s not the direct result of cross-species reassortment. NA and MP seem to be the new players, and they’re pure swine (based on BLAST of A/California/04/2009).
I would love for the media to explain (or at least evince an understanding) of the interplay between R0 and mortality rate. Instead, the coverage seems to veer wildly between “ZOMG WEER AL GOONA DIE!” to “What, me worry?” I fully expect the former to win out over the latter as more clusters appear.
April 30th, 2009 at 11:53 am
Petr, that’s one of the weakest responses I’ve ever seen from someone who has been clearly shown to be mistaken.
You might try admitting that although your definition of pandemic was a reasonable guess, based on the etymology of the word, it is not the definition used by public health professionals. Nor used by anyone in the world except you, as far as I can tell.
April 30th, 2009 at 11:57 am
Well, perhaps there will be a day when the media evince even the foggiest understanding of any aspect of science, but (with the exception of the few remaining science reporters employed by a tiny handful of major media outlets like the NYT) I don’t expect that I’ll live to see it.
April 30th, 2009 at 12:01 pm
There are less confirmed cases in the entire U.S. than I personally know people who had the “regular” flu this year.
You personally know 110 or more people who had regular flu this year?
April 30th, 2009 at 12:28 pm
The under-rated MI:2 was a good primer for flu. The chief reservoirs for flu are pigs, ducks, and people. China mingles these together in sufficient numbers to be the source for most of our flu strains. (The Hong Kong artist John Woo kept the face of China hidden, but he kept images of mutation front and center. Count the number of English accents, for example.)
We now return to our world-saving deliberations.
April 30th, 2009 at 12:47 pm
Jeffrey,
Actually, most of the closest genetic relatives to the current H1N1 strain are from the upper Midwest (NS, NP, HA, PA, PB1, PB2). There’s also a couple of European strains in there (NA,MP) whose reassortment chain CDC can’t figure out yet. (MP does have some Asian cousins out there.) We probably exported the constituent viruses abroad, where they reassorted and came back. (This also means that its appearance in Mexico was almost certainly just very bad luck for them, exacerbated by environmental issues such as Mexico City shutting off water to its population for 36 hours.)
April 30th, 2009 at 1:01 pm
If I cared at all what you thought of me, I’d demand an apology. If you care at all about anybody, then please think and read before you speak. And don’t misinform First, do no harm.
Try telling that to the WHO, who describe the phases of a pandemic thusly[1]:
That’s a pretty bright and shiny line connecting ANIMAL viruses and HUMANS and is NOT the definition they use regarding epidemics. You’re wrong. The other guy (wasisname?) is wrong. A pandemic IS NOT simply an epidemic only order of magnitudes larger. Please stop spreading misinformation.
It’s thinking and logic like that which leads people to fear that any cough, sniffle or fever either IS deadly or CAN BECOME deadly.
So, to be clear, the WHO, the authority on global public health, defines a pandemic in terms of when and where an animal virus subtype enters a human community and becomes transmissible from human to human in new and very unpredictable ways. Go figure. (http://www.who.int/csr/disease/avian_influenza/phase/en/)
You ought to ask yourself why it is you are so insistent on my being wrong. That’s a sign of something dangerous, you know…
April 30th, 2009 at 1:17 pm
petr,
Just to be clear, the WHO definition you cite is specific to influenza. Technically, an epidemic denotes morbidity over baseline for a specific period of time in a community or region. A pandemic, in turn, can also be called a “global epidemic:” an epidemic over a massive region, generally showing incredibly high morbidity.
Influenza is slightly different because the flu virus is very, very good at what’s called “reassortment,” a kind of genetic mix-and-match in which different flu viruses exchange genes, creating novel strains. This happens extensively in the animal population, where birds act as reservoirs. Pigs share receptors with both birds and humans, so they can act as a “mixing bowl” in which avian, swine and human strains can interact. Thus, novel influenza strains generally emerge as zoonoses, and pandemics are almost be definition caused by zoonotic strains, because humans will not have immunoprotection.
All this is quibbling at best: you (and the other posters) are basically on agreement on the important points, and we should focus on those. Concern, but not panic, is warranted at this time.
April 30th, 2009 at 1:28 pm
Once again, that’s not the definition of “pandemic”. It’s the mechanism by which FLU pandemics come about, as has already been explained to you. Furthermore, your summary isn’t even accurate, because you don’t understand the material to which you linked. Once a flu virus acquires the ability to spread from human to human its transmission isn’t “new and unpredictable”, it’s well understood: same as any flu. (That’s why we know that transmission can be interrupted if people will do things like stay home when they’re sick and wash their hands frequently.)
“Normal” seasonal flu and pandemic flu differ in that there is residual immunity to the former in the population, built up during previous exposures (and/or immunization). The ability to evade that reservoir of immunity is what causes a novel flu virus- once it has acquired the ability to spread directly among humans- to have the potential for causing a pandemic. The serious public health problem posed by a pandemic, even of a flu with “normal” and not 1918-like symptoms, is that a lot more people get sick than in a regular flu season, and there can be multiple waves of illness before the pandemic subsides.
April 30th, 2009 at 1:37 pm
As far as I can tell, CDC doesn’t yet have a reproduction rate (R0) defined for this virus. Is that true? My understanding is that flus with R0 less than 1.4 can be suppressed with anti-virals but when R0 is around 2 that is no longer possible.
Also, that while R0 can obviously be depressed by measures like social distancing, the inherent R0 characteristic of a flu virus tends to rise as the virus adapts to the human population
(i.e becomes more contagious as time goes on until the surviving population begins to develop partial immunity.)
With R0 equal to 2, then 10 initial cases become 30 in about 3 days. The 30 become 70 three days later. Then 150 etc.
Which is not alarming , initially. It when you have 10 million becoming 30 million, 30 million then becoming 70 million, 7 million becoming 150 million etc on 3 day periods that things get interesting at the hospital.
There is also the issue of death rates. 1 death out of 100 cases doesn’t seem deadly at first –until you realize that equals 3 million out of a population of 300 million.
Also, a guy at Northwestern has a model which projects outbreaks expanding outward from the major airports. His projection for number of US cases 28 days from now is around 1700 people. Hopefully, the onset of summer will depress the spread and buy us 3 or 4 months of time.
April 30th, 2009 at 1:39 pm
You ought to ask yourself why you are so invested in being right about a subject which you clearly have only recent acquaintance.
Relax. It’s okay to be wrong every once in a while. It’s even okay to be stubborn in refusing to recognize you’re wrong…every once in a while. Your definition of pandemic is wrong. It undoubtedly arose from a slight misunderstanding of something you read which was specific to the flu, as tWB implies.
April 30th, 2009 at 1:47 pm
True enough. But the general ‘pandemic preparedness’ outline, which mirrors what I posted but which isn’t limited to influenza and was originally seen (at least by me) in a PDF, whose original URL, I’ve misplaced.
As I’ve been at pains to point out, I don’t think this is correct. Or, at least, is correct only at the most superficial level. I stand by what I consider the original meaning of the prefix ‘pan-’, throughout and across species. As such, it’s different from an epidemic which, as you’ve noted is characterized by a specific disease causing excess morbidity in a proscribed region. Often an epidemic can show increase morbidity as a result of low immunity against specific strains, but a pandemic is characterized by high mutability of the strain. Which is something else entirely.
You may have the ‘armor’ to fight of the ‘regular’ flu. Well and good. Don’t be fooled by the similarities in symptomology, it may be a different beast altogether and it may, in fact, outpace your ”armor’ altogether. Consider: As you correctly note, the melange of genes from separate species creates opportunities for breakneck pace of mutagenic capacity. As may have been the case in 1918, the health and efficacy of individuals immune systems might be irrelevant, or even counter-productive, to morbidity rates. This is not the case, as I understand it, in an epidemic, where much depends upon immune system response. You rightly highlight ‘reassortment’ as a danger. Well, reassortment can either bypass or usurp your immune system.
It’s the difference between a strong, but steady, target and a fast moving one… Much will depend on proper public policy and I hope to heaven that policy doesn’t derive from the logic that thinking we can just attack it like an epidemic, only bigger and more so… I think that’s wrong.
April 30th, 2009 at 1:59 pm
My understanding is that total body counts from a flu virus can come from two effects: (a) the deadliness of the virus –i.e., what percentage of its victims die and (b) the contagiousness of the virus — i.e., what percentage of people exposed to it become ill and in turn pass that illness on.
A new form of a virus that is highly contagious may not be particularly deadly but can still kill a lot of people simply because an abnormally high number of people become ill.
An additional issue is whether there are other transmission vectors for the flu in addition to sick humans. The concern re avian flu, for example, is that it could be spread widely by migratory geese. So that clusters of disease would keep cropping up even if you suppressed initial outbreaks with quarantines and antivirals. But aren’t there other forms of human flu which are not easily contracted by animal reservoirs?
April 30th, 2009 at 1:59 pm
How many different ways can you get this wrong? Honestly, I’d be a lot more comforted if you were right. But I know you’re not.
‘…only more so’ only gets you so far. High mutability on the part of the strain gets you to pandemic. You can face down a tidal wave, and try to swim… but there’s no possible way you can prepare for a tidal wave that’s about to turn into an earthquake, which will in turn set off a volcano.
Is that going to (definitively) happen? No. But with a pandemic, there’s no way to be certain it isn’t. That’s the really scary thing about pandemics.
April 30th, 2009 at 2:07 pm
The prevailing theory about the evolution of pathogens which cause epidemics, as several people above relate, is that they jump species—an endemic infection in, say, an agricultural species slightly mutates so that it’s viable in humans and because humans have little or no immunity, an epidemic of a virulent disease arises.
Recent research strongly validates this with regard to the 1918 flu epidemic, as well as with HIV. And we know this is the case with past avian and swine flus.
However, if you’ve read my comments on this subject before, you’re aware that I’m a fan of biologist Paul Eward’s evolution of virulence theory, as found in his 1996 book, The Evolution of Infectious Disease. In it, he speculated at length on alternative origins of both the 1918 flu and HIV (speculation which has proven to be wrong) as case studies of his theory. Though these two examples are now known to be inapt, others—specifically virulence outbreaks in hospital neonatal units, as well as the general case of pathogen virulence in hospitals—strongly imply that his general theory is sound.
His theory is that rather than being static or inevitably pushed toward benignity (which conventional theory expects of endemic pathogens), there are environmental factors which can greatly alter evolutionary selection for/against virulence in pathogens, allowing endemic pathogens to unexpectedly become very virulent. The key idea of his theory involves transmission vectors. If the host is the primary transmission vector, then a pathogen will evolve toward less virulence, as expected. A mostly healthy and ambulatory host allows efficient transmission of the pathogen. A suddenly dead host does not.
On the other hand, where the primary transmission vector is an agent other than the host, then there is much reduced selection pressure against virulence. Malaria’s mosquito vector and dysentary’s contaminated water vector are two good examples. In neonatal units and hospitals, it’s nurses and doctors. Otherwise mild pathogens can become very virulent when they can spread independently of its primary host.
Ewald hypothesized that the 1918 flue was an endemic flu that evolved toward extreme virulence in the unusual conditions of the WWI trenches. Immune-compromised soldiers in extremely close proximity, moved from battlefields to crowded hospitals, allowed an otherwise fairly mild flu variant to evolve toward much greater virulence. It’s a compelling narrative…unfortunately, I understand, false.
However, this doesn’t mean that this hasn’t happened or couldn’t happen. The interspecies model of disease infection and virulence is valid and has described over and over again modern epidemics. But it’s not the last word on the subject and it’s a mistake to think that disease epidemics necessarily involve cross-species infection.
April 30th, 2009 at 2:12 pm
Petr, this may be news to you, but a word is not defined by its etymology.
April 30th, 2009 at 2:17 pm
I think the 1918 flu was much more than simply normal flu which got out of hand in bad environmental conditions.
My wife’s grandfather contracted it while a young man on a farm in northern Pennsylvania. Her great aunts told her mother of what a horrible experience it was — of him choking on massive amounts of phlegm –although he survived because they had the idea to turn him upside down to allow his lungs to drain. It was definitely not the common flu.
April 30th, 2009 at 2:24 pm
Keith M Ellis, this may be news to you, but etymologies are important to the definition of a word.
But feel free to call it something else. Call it a banana daiqiri, if you want. My point is that what the WHO and the CDC are calling a ‘pandemic’ is different from what they would (have) called an ‘epidemic’.
My worry, such as it is, is that a whole bunch of congresscritters and their assorted aides are, right now, combing through stacks and stacks of emergency preparedness policy papers furtively scratching out every instance of the word ‘epidemic’ and replacing it with the word ‘pandemic’. They do this because the logic says that an ‘pandemic’ is just an ‘epidemic’ writ large.
I suppose you could go through “War and Peace” and scratch out every instance of ‘cannon’ and replace it with ‘nuclear weapon’ without changing, too much, the gist of the story, no?
If you’re comfortable with that… ok, then. I am not.
April 30th, 2009 at 2:52 pm
At the risk of being called an alarmist nobody really knows yet how severe or mild this flu virus actually is yet. A vaccine is months away, it is a new and unusual strain combining three viral “parents:” Swine, avian and human. It has already killed young healthy adults which is unusual in the extreme for the viruses we see on a yearly basis. It has been suggested that this may be because their immune systems over react and produce too many antibodies, but the jury is still out on that. In fact what we do not know about this virus is exactly what is cause for concern. I am not suggesting we panic because that certainly won’t improve the situation, but suggesting everything is just hunky dory is a really bad idea. I suggest encouraging people to get and stay informed is the only really responsible position to take under these conditions.
April 30th, 2009 at 2:58 pm
Well, in fact, you’re right. From genetic analysis of preserved pathogens (or antibodies?), it was a cross-species mutation.
But your anecdote doesn’t demonstrate anything other than that the 1918 flu was very virulent. A pathogen doesn’t need to mutate that greatly for its virulence to greatly change. Virulence is the combination of many different factors, a lack of an immune response (because its a novel infection) is only one of them.
Virulence is just the by-product of the pathogen’s life-cycle in its host in combination with the host’s response to it. Something as simple as its rate of reproduction in the host affects virulence greatly. Imagine two mutation of the same pathogen, one which reproduces as quickly as it possibly can, and one more slowly. The former might reproduce so quickly that it kills the host before it can spread to another host; the latter might not. The former mutated form will meet its evolutionary end; the latter will not.
Traditional disease theory has long believed that pathogens evolve steadily toward benignity and symbiosis though such processes—that’s the primary reason that virulent diseases were thought to be cross-species mutations long before there was any genetic evidence for this. And, indeed, recent genetic techniques have demonstrated that this seems to usually be the case.
However, there are some endemic human diseases which significantly deviate from this pattern, malaria and dysentery chief among them. Why do those pathogens remain so stubbornly virulent? Ewald has an explanation; and that explanation opens a door on some other contemporary urgent questions, such as the emergence of extremely virulent varieties of otherwise mild pathogens in hospitals.
Petr, the technical definition of pandemic does not rely upon cross-species infection. IT DOES NOT. Your WHO excerpt describes the typical progression of a flu pandemic, and that typical particular progression involves cross-species infection. However, it need not involve a cross-species infection.
Furthermore, the cross-species infection is the genesis of the new mutation, it’s not a necessary requirement of an epidemic or a pandemic that such cross-species infection continue.
It puzzles me, and I’m sure the others who are arguing with you, that you are so obsessed with this. Your argument has all the hallmarks of someone who knows only just enough to inadvertently make a fool of himself. I’d wager that you had this exactly argument—or otherwise “knowingly” educated someone else on the difference between an epidemic and an pandemic—within the last few days.
Just gracefully give up your investment in what is, I promise, a wrong belief. I mentioned the inadequacies of etymologically derived definitions on the basis of my own sorry experience. As someone who’s academically studied classic Greek, for some reason I latched onto an etymologically-derived and hyper-literal definition of the word hypocrite. Someone eventually told me I was wrong. I had a hard time admitting it; I thought I was both smarter and more educated than the person contradicting me. I probably was…nevertheless, I was wrong. You’re wrong about the technical definition of pandemic. Deal with it.
Incidentally, a great many words have contemporary meanings completely at odds with their etymological roots. Language isn’t mathematics.
April 30th, 2009 at 4:01 pm
I’m very certain your puzzlement matters very little to me, nor does your assessment of any recent conversations you think I may have had. You think I’m wrong. Very well. You said your piece. Fine. Done. Move along.
Me, I’m ‘obsessed’ with what is real. And you, and others, continually talking past me, whilst simultaneously attempting to pat me on the head in a rather patronizing manner, all the while misinforming both yourselves and others, is real. Get over yourself.
Honestly.
I don’t particularly care what you call it. I care, as I have been at particular pains to point out again and again, that you don’t confuse it for what it isn’t. Call it a ‘pandemic’. Call it a buggle-futzen-katzenjammer. I don’t care, just don’t call it what it isn’t. Apandemic is not ’simply a bigger epidemic”. That’s painfully simpleminded logic and you (and others) are using it, and torturous elisions to put me down and that is, I think, dangerous. Should I not say so? Should I bow to your egregious paternalism, Dad? No thanks. I’ll speak my mind. You don’t like, you are perfectly free to disagree and move on. But Public policy that derives from this simpleminded and erroneous characterization has the possibility to do harm.
Would you go to a doctor who treats that gangrenous wound as a giant hangnail? Of course you wouldn’t. But you don’t let that stop you from throwing around cheap equivalances without meaning but with possible consequences.
Honestly, do you want to see policy made on such simple minded elisions? If I’m obsessed about anything it’s that we don’t screw this up! I’m not sanguine…
April 30th, 2009 at 4:02 pm
The numbers are small and come almost entirely from Mexico where there just aren’t good data on the total number of infections.
I’m cautiously optimistic on this aspect of it. There is no real evidence of unusual virulence, nor any of the presence in the virus of sequences known to associated with such virulence.
Still a pandemic of “normal” flu is a very serious matter and will lead to a lot of deaths. Seasonal flu kills a lot more people than most people realize and we should probably worry about THAT more than we do. Multiply that by the rapid pandemic spread of an immunologically novel virus and you’ve got an event that’s plenty bad.
April 30th, 2009 at 4:15 pm
Petr — “A pandemic IS NOT simply an epidemic only order of magnitudes larger.”
True. But I never said it was. The person you were responding to in your original post was wrong.
However, your “correction” was also wrong.
You said: “An epidemic, as it is ‘traditionally’ thougt of, is confined to a single species (usually humans) and, it is thought, that the mutations seen, however, are limited to the mutations possible within that single species… A pandemic, however, is a disease that can jump from species to species.”
This is simply not accurate. Not by the definitions provided by others, and not even according to your own source. It is misinformation. By your very own standards, you are doing harm by providing this misinformation to people.
The ability to jump between species is one of the factors that differentiates between various risk phases in the WHO classification of flu pandemics. However, the ability to jump from animals to humans is not the distinction between an epidemic and a pandemic, as your own source makes explicitly clear.
In fact, it is community level outbreaks, spread by human to human contact, in multiple regions of the globe, that characterizes a pandemic and distinguishes it from an epidemic. Not “jumping from one species to another”, which is a characteristic trait of nearly all flu epidemics, and is not a necessary characteristic of other pandemic diseases.
In short, you are wrong, you have discredited yourself with your own quote, and you are either too stubborn or too clueless to realize this.
April 30th, 2009 at 4:36 pm
For the sake of clarity, I should point out that mutation in an animal host, following by a subsequent jump to humans, really is an important warning sign for a flu pandemic. This is because lethal viral epidemics break out when a novel strain of a virus emerges, to which the population has no immunity, and cross-species mutation is the most common of several important ways by which novel strains may emerge.
But this is NOT the distinction between an epidemic and a pandemic. The “pan”, in this case, means “global”. It is possible to have an epidemic outbreak of swine flu or bird flu that does not become a pandemic.
But don’t take my word for it:
Wikipedia: “A pandemic (from Greek παν pan all + δήμος demos people) is an epidemic of infectious disease that spreads through populations across a large region; for instance a continent, or even worldwide.”
American Heritage Dictionary: “Epidemic over a wide geographic area and affecting a large proportion of the population”
MediLexicon: “Denoting a disease affecting or attacking the population of an extensive region, country, continent, global; extensively epidemic.”
April 30th, 2009 at 4:41 pm
Don:
R0 is estimated from data, assumptions about contact patterns and known aspects of the disease, so there’s never a truly *defined* R0 for a disease, just a value that’s estimated for the purposes of a particular model.
For example, I can use the La Gloria infection data to make a rough estimate of R0 as 4.77824 (with a bunch of fairly aggressive assumptions rolled into that estimate), but most pandemic and inter-pandemic influenza strains are generally estimated to fall between an R0 of 3 and 4. The 1918 strain was relatively slow-growing, with most estimates of R0 between 1.8 and 3. An R0 of around 5 would make it an aggressive disease by flu standards, but not particularly fast-spreading compared to, say, measles.
Whether a disease can be adequately controlled with antivirals (or immunization) before it grows to an unmanageable level is a question that is dependent on the model developed for that disease. For example, Longini et al model H5N1 responses and find that their simulation allows for successful antiviral prophylaxis for human-transmissive avian flu with an R0 up to 1.6.
But it’s damned hard to drop the Tamiflu blanket over every cluster outbreak area when a pandemic is going on. With 39 countries suspecting active H1N1 infections, it’s just not possible to use antiviral prophylaxis to smother the pandemic. Instead, it’ll be administered to high-risk populations in an effort to reduce the mortality rate.
April 30th, 2009 at 4:46 pm
What an extraordinarily facile quibble… Next you’re gonna tell me it’s not a pregnancy until a diaper has to be changed…
But, I suppose if we can at least begin to agree on that a pandemic is different, in both degree and kind, from a epidemic, that’s something. I will agree that the are fairly broad terms, applied indescriminately and often. This I lament.
April 30th, 2009 at 4:54 pm
So let me get this straight…
You provide a confusing pseudo-explanation of the difference between an epidemic and pandemic, in which attempt with some veneer of authority to misinform people. But your explanation contains a distorted element of the truth. And it’s “an extraordinarily facile quibble” for me to point this out.
And yet you jumped all over someone else here and lectured them (inaccurately) for saying that the difference between an epidemic and a pandemic is one of magnitude, when in fact the difference is geographic distribution. Now THAT is a quibble. If you had gotten the answer right yourself, this would be a perfectly reasonable thing to do… politely. But hardly the sort of inaccuracy that warrants condescension and self-important hectoring about “doing no harm.”
And then you got the answer even wronger. Instant karma, I guess.
April 30th, 2009 at 5:24 pm
LaFollette, I did not say “larger”. I said, correctly, “more widespread” (meaning geographically).
April 30th, 2009 at 6:28 pm
Re: If you are looking at the flu epidemic of 1918/1919, that is actually the correct advice.
1918-1919 featured some unusual circumstances: a long-running brutal war that left millions of people (soldiers and civilans both) malnourished and living in unsanitary conditions. I would suggest that a flu pandemic now would be more likely to resemble the pandemics of 1957 and 1968 about which there seems to be no cultural memory at all.
April 30th, 2009 at 10:08 pm
I’m inclined to agree with most of the commenters that when you’re faced with a novel strain of influenza of unknown virulence and reproduction rate (promiscuity?), a little fretting is in order. On the other hand, it’s possible Matt and the default-cynical gawker-media crowd is correct. If so, it will be the CDC, WHO, UN & c. who owe us an apology rather than the media. When experts are rattling their cages as much as they have been this week, I want the media to pay attention.
May 1st, 2009 at 8:04 am
Isn’t the definition of “epidemic” Higher than normal? Normal being 36ooo annual deaths, how is ZERO US deaths an epidemic? Why does the government need 1.5 BILLION tax dollars to combat maybe 300 people with the flu?
May 1st, 2009 at 11:14 am
Sorry about that, Steve. I made the mistake of assuming that Petr was responding to someone on the thread and characterizing what they said fairly. I now see that he was distorting your correct assessment. Should’ve known better.
May 1st, 2009 at 12:16 pm
The answer
The one thing that will both help to check panic over a swine flu outbreak that is not likely to do much more than it has aready, and will help us get a more appropriate response to the very real, much more extensive and destuctive pandemic of “normal” flu we have every year, is to always tie them together.
For example, if we see a school district deciding to shut down their schools in order to slow the spread of swine flu, we should set this idea against the risk/benefits of doing this every year, for the annual normal flu pandemic. There have not been any reports of anyone of school age dying of this Swine Flu, so the idea behind shutting schools is presumably that schools are an excellent way to spread the flu throughout the whole population, including those ages that have seen deaths, therefore ending this route of broadcast transmission will save lives. That isn’t a bad, or groundless, thought. But if closing the schools is a reasonable price to pay for an outbreak that probably won’t break 1,000 deaths, why wouldn’t we do that evey flu season when we face a near-certainty of >30,000 deaths from flu? Why not move the summer school vacation so that it starts in December, and thus throws a wrench into flu’s game plan for killing 36,000 of us each and every year? The latter actually makes some sense, and is not offered as a reductio ad absurdam to get people off the idea of shutting schools now. But what does seem to me absurd, is to shut schools for Swine Flu, when you’re not even talkiing about shutting them for a surer, bigger killer.
Ditto for the vaccine against Swine Flu that we are probably going to see rushed into production. The plan is to give it to everybody, which again, is not a bad idea. But if vaccinating everyone for this so-far piddling Swine Flu makes sense, as a safety play against it possibly taking off, why is it not even more sensible to vaccinate everyone every year against the normal flu that normally does take off to the tune of 36,000 dead? We now confine the recommended vaccination only to those at risk of death, ignoring the role that the rest of the popuation plays at putting these people at risk of death. Again, this is not a reductio. We should be vaccinating everyone every year.
We let 3,000 deaths in 2001 push us into practically changing our form of government, but >30,000 deaths year after year, and we can’t even change the school calendar, or vaccinate everyone. Let’s get some perspective back in our risk assessments.
May 1st, 2009 at 5:55 pm
I’d really like to know where that 1.5 Billion is going. I sure hope its not going any where near pharmisutical lobbyists. Still don’t understand why the government would start a panic over something this minor, relatively speaking.