The puzzle of the age distribution of H5N1 cases

A paper that appeared a week ago seems to have made its way to the wires. I had intended to post on it but didn't get around to it. But I guess the time has come.

Two medical geographers have written a letter to CDC's journal, Emerging Infectious Diseases, about what many have already observed: 90% of the WHO cases of H5N1 in humans are under the age of 40 years old. Using information on 169 of the current 271 cases, Matthew Smallman-Raynor and Andrew D. Cliff, medical geographers at the Universities of Nottingham and Cambridge in the UK find:

Subject to multiple selection biases in the identification and reporting of WHO-confirmed human cases of avian influenza A (H5N1), our analysis yields 3 noteworthy observations: 1) case counts and case rates suggest similar levels of disease activity in the age categories 0-9, 10-19, and 20-29 years; 2) few cases have occurred above the age band of 30-35 years; and 3) the skewed distribution of cases toward children and young adults transcends sex, reporting period, patient outcome, geographic location, and, by implication, local cultural and demographic determinants. (Emerging Infectious Diseases, cite omitted)

Explanation? One obvious possibility is that the observed age distribution is just a reflection of the age structures of the populations among which the cases arose. WHO has also just published some descriptive epidemiology of the confirmed cases. The cases series overlaps with the EID series but is not identical. Since individual countries have different age structures and the number of cases in any one country is usually not high, WHO was not able to say definitively that the observed results were not just due to population structure, but the evidence suggests not. So what else is there?

There may be behavioral differences in exposure that make it more likely younger people are exposed to whatever is the reservoir in nature (currently considered to be infected domestic poultry). There are conflicting opinions as to whether such differences exist, or at least, whether they are sufficient to explain the data. The fact that the same age distribution of cases seems to be roughly seen across borders and cultures argues for other factors. The authors of the EID paper suggest that widespread immunity among older individuals among persons born before 1969. So far, however, there is no serologic evidence of this, but the data are scant.

Yet another possibility (and one we favor) is that the unusualness of the disease is less obvious in older individuals for reasons unrelated to prior exposure but possibly related to different immunological or other biological responses to infection (e.g., cross reactivity with other infections). Serious and rapidly evolving respiratory disease in a young and healthy person attracts considerably more attention than in the elderly.This could result in reduced ascertainment of respiratory disease against a background of high prevalence from the usual circulating respiratory viruses in the older age groups. Diagnosis of H5N1 infection depends critically on index of suspicion, a threshold likely met in only a small proportion of influenza-like illnesses which might be H5N1 and less so among older patients than younger. If the disease in the over 40 age group is also somewhat less severe, this could impart an ascertainment bias and the question of whether the cases match the age structure of the population would again be something to consider.

Both papers have graphs of the age distribution, but here is another one from WHO's Western Pacific Regional Office which illustrates the data nicely:

i-dbf94ecd4ae21539362278acc562c2bc-S4_0130_456x342.shkl.jpg

Source: WHO WPRO

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Weren't young, healthy folks most likely to die from the 1918 flu because their immune systems responded too strongly? Could something like that be happening here?

On the other hand Revere, Tan06 pointed out to me that having lived in Indon for several years, a 40 year old guy is considered to be pretty old. They shuffle off in great numbers about that age and more so in the boonies of Sumatera/Java. Very disparate age groupings from the cities to the outlying areas. Something like a 2 - 1 ratio for people in the boonies opposed to the cities.

Might be something else to consider in this age grouping thing. Same applies in Turkey. Both countries have about a 65-67 life span for both males and females and very disparate between the cities and village .

By M. Randolph Kruger (not verified) on 11 Feb 2007 #permalink

Jane: The reason the young died more often is still a matter of debate and contention. The "over active immune system" (aka cytokine storm) hypothesis is one possible explanation but it isn't really much of an explanation since we don't what this means exactly. Whatever the reason, it is likely that the same thing is at work here. We discussed it here,, here, here, here, here, and at our piece at Flu Wiki, among other places on this site and our previous venue (effectmeasure.blogspot.com).

If there really is some protective cross-immunity in folk over 40 in the areas currently hit by bird flu, that doesn't necessarily mean that we here over 40 can work a panflu with impunity; the reason H5N1 is nailing folk there now is because they live in close proximity to chickens, and have done so for generations. Just because the local chicken farmer in Jakarta 40 years ago got LPAI H5N1 conjunctivitis and forgot about it, doesn't mean that 40 year olds in the first world have any immunity at all.

I think we need to resist generalizing about this. Scientific method--observation, hypothesis, experiment, data, conclusion--at this point we have an observation and a hypothesis, but no experiments (ie: serology) and data to reach a conclusion.

By Lisa the GP (not verified) on 11 Feb 2007 #permalink

I believe the reason is higher metabolism and therefore slightly higher body temperature which exceeds a threshold for virus infectivity.

Secondly, there may be an age difference in the relative susceptibility by 2-3 vs. 2-6 receptors by cell type.

This story sound a lot like more 'spin' to me...

...Don't worry, be happy...no one over thirty is going to get it.

In January 2006, everyone was also convinced that there were widespread asymptomatic infections.

The first step for an alcoholic is to admit they have a drinking problem...I wish responsible authorities would do the same with respect to H5N1 and pandemic influenza in general...and then we might get something productive done.

Tom: I'm not following. Is this sarcasm or a theory? Or what?

Sorry Revere.

In Jan 2006, we were told that the CFR wasn't in reality high at all, that there were widespread asymptomatic infections...

In Apr. we were told that the explanation for Karo was that there was a familial genetic susceptibility to H5N1 infection...

And now we are being told that in all likelyhood, those over thirty are protected because of some 'phantom' influenza infection from the distant past...

In my opinion and it is only my opinion...more spin...more hooey.

I believe that the reason is due to metabolism and resultant slight changes in body temperature...pregnant women would also have higher metabolism as well.

Secondly, I believe that relative cell based receptor efficiency and activity varies with age...this does happen with animal physiology.

I also believe that this is an evolutionary tool of influenza viruses. If they attack those with relatively high body temperatures then they are, in fact, selectively choosing children or adults with co-infections with seasonal influenza...providing the mixing ground for recombinations etc.

I also believe that adults would have a normal distributon in body metabolism as well...and this could explain why some adults are infected while a majority to this point are not.

Finally, this virus is currently an adolescent. I expect that as it matures it will make the whole population susceptible.

In my opinion, and it is only my opinion, because of a lot of spin...regulators and governments do not believe at all that we are susceptible to or are going to have a pandemic in their working lifetimes...

...some one had better smarten them up...we are running out of 'God's time'.

Tom: The "prior immunization" theory (which I do not subscribe to) is from two medical geographers from universities in the UK. I'm not sure how that qualifies as spin since they speak for no one but themselves. It also doesn't affect the CFR. If you are immune you are not counted in the CFR, which is a conditional probability. You have to be infected first. Immunity in the population might affect the attack rate but not the CFR.

Revere.

Any fragment of information from any source that offers an opening to downplay the threat of a pandemic is jumped on...if the last thirteen months is the template.

It may make political sense but it sure does not make scientific or ethical sense, in my opinion...

...a 'fools' game...buying short term gain in exchange for long term pain, in my opinion.

Tom: Errr.....I don't get it. Are you saying this should not have been published? Are you saying any view that you think damps down the threat (by your accounting) shouldn't be allowed? What about sequences that don't show a mutation? Suppressed? Scientific papers that show Tamiflu may be effective? Suppressed? Denigrated? What?

Revere. I would hope that you would not think me such a 'kook' to want to suppress ethical science.

In this day and age, unfortunately, we need to know who funded a study.

Other than that the study is not the problem...it is what happens after...how the scientific truth is manipulated...and in the case of H5N1, this has been done repeatedly...fluff up the news downplaying a pandemic and suppress the news in the other direction.

In my professional life I have not seen anything like it...maybe it is normal for others...I don't know.

By the way, there has been a lot of suppression of sequences so I wouldn't have a clue one way or another, if there were mutations at all...shouldn't you be talking to the spinners about that rather than some farm veterinarian from the sticks.

...and, I haven't seen any journal articles with statistically significant benefits to Tamiflu. /:0)

This claim, even if statistically proven, does nothing to relieve my concern. Great, I might live through a pandemic while my children, nieces, nephews and godchildren (and all of yours too) may not. If someone is using reports to spin pandemic flu information, they could do a little better than this.

If someone is using reports to spin pandemic flu information, it is probably for the purpose of influencing vaccine priorities such that nobody over 40 gets a shot.

By Lisa_the GP (not verified) on 11 Feb 2007 #permalink

Lisa-Duly noted. Most doctors by the time they become street legal are just about 30 plus.So I would say most doctors wouldnt get the shot except for the fact that they are doctors. My understanding is that doctors/HCW would be breeding grounds for the bug. They'll leave their families and many of them will not return.

Tom-This over 40 thing is spin. Nothing I have seen to definitively back that noise up. The Gubernator is requesting the legislature to authorize the purchase of a lot of ventilators for bird flu patients, but with no one to run the things. It is as you and Lisa say, basically putting a shiny bow tie on a goat. Its still a goat afterwards. So far looking at the flu treatment and post flu cases its very apparent that even with a ventilator your chances might only increase by a max of 5% and thats being charitable. No one has shown me anything from my side of the fence to indicate that the power grids to run them wont snap.

Spin-This is IMO the biggest case of it in history. I think they know its coming and its going to be a hard case. CDC's Gerberdinator is not the brightest bulb in the socket and they could do better. They dont want to panic everyone but he who isnt prepared is going to take it in the shorts. With just a little preparation even a single mom with three kids could make it thru this like a breeze but they are sitting back and soft pedaling it in the face of a graph that continues to climb north in a hard, fast messy way and thats from the cases we know about. What happened to those 6500 in China from three years ago?

40? It looks to me if you get a reportable case for any age group you are one leg into the box and publishing a story with that buffer zone with no science behind it except for some fluff is very dangerous. I dont know whether any of you have been following post flu bacterial pneumonia's but its about 25% of the survivors of the flu. So you survive bird flu only to die of bacterial pneumonia a couple of days later. If it is spin we are in deep, deep trouble I and wouldnt want to have MD or even DVM behind my name in a phone book.

By M. Randolph Kruger (not verified) on 12 Feb 2007 #permalink

Over 40 immune? Hey thats great news! Now i dont have to worry about getting sick. I am over 40. The CDC is taking care of everything. They will close the schools and we will keep our kids home safe and sound. I can continue to go to work and keep the economy humming along - Business as usual. Nah, no spin here folks... just a positive note in a bad symphony.

Won't need to prep either since we will all be working and the shelves will be stocked.

As I said months ago, they'd rather take the viral hit than the collateral hit.

Dear Revere,
While I agree that young healthy people with rapidly progressive disease may be more likely to come to medical attention, it is my understanding that (unpublished) serological studies among contacts of cases (presumably of all ages) did not indicate that many cases were being missed.

epifreek: Yes, this is true. But these aren't necessarily the kind of inapparent cases you pick up in a seroprevalence survey. They are clinical cases, like the confirmed cases, that are never diagnosed for agent. Assuming that a certain percentage of the pneumonia deaths are H5N1 that were never worked up, it is plausible there are more among the elderly. So this is observation bias.

Wouldn't "prior immunization" show up in H5N1 serology studies ?

timf: There are few such studies at the moment. Also the level of antibodies that would be protective in the absence of challenge isn't clear, so this isn't definitive. However I don't favor the immunity theory, as I made clear.

In news stories about bird flu deaths they often say that people who are in close proximity to sick birds are vmore likely to get sick.I have heard news stories about sick children that the were playing with dead chickens and many children who slaughter chickens are probably not as carefull as adults would be.I have even seen pictures of children standing on a pile of culled chickens.Most people over 35 would not engage in these activities.Could this be at least partially the reason for more yonger people getting sick.

Wayne: No one knows why some people get it and not others. Exposure to sick birds is a risk factor, but it is also highly prevalent in countries where there are human cases. About third of the cases in Vietnam and Indon also don't have good histories of close contact with sick birds, although this is repeated over and over again. If there is a sick bird within shouting distance they count it.

Age related exposure differences has been talked about as an explanation, but the same picture across continents and cultures seems to argue against behavioral explanations. But who knows?

Dr. Niman is reporting that the most recently released Indonesian poultry sequences DO match the human sequences.

A little new math here. Take the cases above 40 to graph end. It comes up with a total of 30 cases dead or alive. Out of that, 19 were alive and 11 were dead. So about 1/3rd survived it. This in some cases was with extraordinary care that wont be available when the bug arrives in HP fashion. So for right now you old guys (40 on up, men and women) you can expect that you have a 1/3rd chance of putting one leg into the box. This is unevenly distributed but the lack of available care would likely even that number out to a very smooth graph and probably bring the numbers up a bit on the dead so lets say you have a 40% chance of not making. Interesting. This of course doesnt take into account secondary causality of death such as starvation, exposure, anarchy, lack of available care or supplies to perform, post flu bacterial pneumonia's.

They are of course soft pedaling this whole thing but that graph keeps climbing and the three known medical types here, well four if you count Grace the RN can read it better than any of us on morbidity. I dont like it continuing to climb because I am a math guy and I ran it out exponentially and if you used SARS as the baseline we will have pandemic in under a year. The time between clusters is shortening and again if you used that as the baseline alone we will see it in less than three months.

Going further, if you go to SE Asia as a baseline and using them as the whole world scenario instead of all the countries and run it using the graphic patterns (subject to interpretation on this one, I dont know for sure what they are using) we are ALREADY in full blown epidemic in an 8 country world. And the graph just keeps climbing. Revere/Lisa/Tom/Grace could address more capably the clusters, but size matters I think looking at it. We have gone from the onesy-twoseys, to the threesy-fourseys, finally to the five and sixies. Now we are seeing 9 possibles starting to pop. Spring is just around the corner and its alive and well down in the S. Hemisphere and they are going into winter. Ought to prove interesting by May/June.

By M. Randolph Kruger (not verified) on 12 Feb 2007 #permalink

"Any fragment of information from any source that offers an opening to downplay the threat of a pandemic is jumped on...if the last thirteen months is the template."

Tom,
Do you not believe that the opposite might also be true? The known facts of the H5N1 situation globally, in relation to a pandemic, would suggest that things are pretty static even though you seem to be saying the opposite. The number of confirmed cases is not going up at a faster rate, even with increased viral spread and surveillance. Dr. David Nabarro, whom you've referenced in the past, said as much last week:

"During the time that I've been in this job, I have seen no increase in the risk of a pandemic"

"The virus does not seem to have evolved in ways that suggest that it's moving towards being more transmissible between humans, the risk is staying about the same"

While you may feel that the virus will ultimately end up as panflu, simply disregarding anything that may challenge your opinion seems rather short sighted.

Shonda Thanks.

I hope that I am not leaving the impression that I am "simply disregarding anything that may challenge my opinion".

As a scientist, and we are all scientists, one must keep an open mind at all times...or as Thomas King, a Native Canadian writer put it...'stay calm, be brave, wait for the signs'.

This is an animal disease and that is why I am qualified to comment...and so are all of the rest of the emerging exotic diseases.

I think it is a little like the youngster who puts his fingers up to his face and assumes that because he cannot see you that you cannot see him...

...The point being that it is what is beyond our senses that is the problem...and not the superficial that we can see.

I think if asked, Dr. Nabarro would say that the threat has not increased because it was high when he came to his job and remains at the same level today. Last fall he was quoted as saying that 'we are on God's time'.

The authorities are downplaying a pandemic because they are convinced it is not going to happen...

...They do jump on any shred of news that allows them to downplay the threat and then make sure it is distributed as far as possible into the public realm.

The World Health Organizations strategy that it isn't going to happen is a good one..if they have based their conclusion on science and not expediency...time will tell.

Hookworm infection anyone?
Age related, in contrast to other worm infestations is more prevalent
in -mature- adult humans, hookworms downregulate the immune system in order to survive.
In 1918 the rate of infestations might have been even more prevalent than now,
with 1 billion+ infected people worldwide would this account for the difference
in CFR with age?

"On contact with the human host, the larvae penetrate the skin and
are carried through the veins to the heart and then to the lungs.
They penetrate into the pulmonary alveoli, ascend the bronchial tree
to the pharynx, and are swallowed . The larvae reach the small
intestine, where they reside and mature into adults"

One may wonder what a respiratory tract carpeted
with those interacts with a flu infection...

Asthma and hayfever have been treated by reinfection with hookworms,
so what about cytokine disregulation?

Lou Dam retreats to Planet Pern, waits for deadly Silver Threads to fall off the sky.

Hi Lou. Interesting concept.

Personally, I don't think that hookworm infection is as common as one might think...in those who are infected, natural resistance should tend to build up.

Usually, when this type of thing crosses species, the life cycle cannot be completed and as a result, I may well have a few nodules in my lungs from cattle worms.

Any co-infection would create problems because it might lower the threshold innoculation dose so to speak. I would be very concerned about HIV.

Also, I wonder how the myriad of chemical molecules, consumed in processed and fast foods daily, depress immune system function. This could make some advanced countries more prone to H5N1.

TomDVM,
I think Dr. Nabarro's comments speak for themselves. The virus is not becoming more transmissible and the number of human cases are not increasing at a faster rate. In fact with increased surveillance and a wider geographic range, the opposite appears to be true. These are scientific facts. You may have opinions of what the virus might become but the current facts do not suggest that the virus is heading towards panflu.

Tom DVM, I am sending here the refs. dugout from the net, please excuse the size as it may not
be the proper place to leave this but I thought it made my point for older people being less
affected by H1N1 (1918) or H5N1 in asfar as cytokine dysregulation is concerned. Lou

From Wikipedia:
Hookworms are thought to infect 800 million people worldwide.

In contrast with most intestinal helminthiases that concentrate parasitic load in children, hookworm prevalence is often higher among adult males. In tropical areas this is associated with high prevalence of anemia among adult men.

[edit] Hookworm in therapy

Moderate hookworm infections have been demonstrated to have beneficial effects on their hosts. Research at the University of Nottingham conducted in Ethiopia has demonstrated that people with hookworm infections are half as likely to experience asthma[1] or hay fever.[2]

The theory is that our immune systems evolved under constant assault from a variety of parasites, most of which have to modulate our immune response to succeed. That is, they have to down regulate the response that would otherwise attack them. Evolving with a down-regulated immune system means that in the absence of those down-regulating parasites our immune systems often attack our own tissues, leading to asthma, hay fever, IBD, colitis, Crohn's and perhaps other autoimmune diseases. Hence the increase in autoimmune diseases in the relatively clean and sterile industrialized world.

From PLoS Medicine Home Page
http://medicine.plosjournals.org/
Hookworm:The Great Infection of Mankind
No international surveillance mechanisms are in place to determine the prevalence and global distribution of hookworm infection. However, based on an extensive search of the literature since 1990, the worldwide number of cases of hookworm was recently estimated to be 740 million people

Compared to other STH infections and schistosomiasis, hookworm infection exhibits a unique age-intensity profile whereas the intensities for the former peak in childhood and adolescence, hookworm intensity usually either steadily rises in intensity with age or plateaus in adulthood. The biological basis for this observation is unknown

From: eMedicine - Hookworm Infection : Article by Christopher M Watson, MD

The absolute number of hookworm infections is highest in China with 203 million followed by sub-Saharan Africa with 198 million. When prevalences are compared, sub-Saharan Africa is highest with 29% of the population infected followed by East Asia, which has a prevalence of 26%. India, South Asia, and Latin America have slightly decreased but still notable infection rates.

Age: Although children bear a large disease burden, hookworm infection appears to have an atypical distribution of infection by age. Unlike other soil-transmitted helminth infections, such as those due to Ascaris or Trichuris organisms, for which the incidence peaks in childhood, hookworm infection appears to continue to increase throughout childhood until it reaches a plateau in adulthood.
----------------------------------------------------------------------------------
Despite their small size, large number, and apparent anatomic simplicity, hookworms continue to evade lasting human immune responses. As part of recent public health efforts to reduce rates of hookworm infection, the evoked immune response has been extensively investigated in both human and animal models. Although hookworm infection stimulates a helper T-cell type-2 response, the role of this response in maintaining or deterring ongoing infection is debated. Levels of immunoglobulin G (IgG) detectably increase in the 2-8 weeks after the primary infection. In addition, in naturally infected populations, levels of all 5 subtypes of immunoglobulins appear elevated, with substantial upregulation of polyclonal immunoglobulin E (IgE). Eosinophilia is commonly observed, peaking at 35-65 days after infection. Hookworm infection also appears to cause upregulation of the cytokine interleukin (IL)-10 and is a proposed mechanism of proinflammatory cytokine suppression.
-----------------------------------------------------------------------------------
The persistent nature of hookworm infection supports the theory that hookworms have evolved adaptive molecular mechanisms to achieve a homeostatic balance with the host immune response. Identified components of the hookworm response include calreticulin, antioxidants, and eotaxin metalloproteinase among others. This modulation of the human immune response by hookworms has also been postulated to reduce the allergenic response of the host, a theory known as the hygiene hypothesis.

Shonda-Your point is taken about the possibility that panflu might not appear. On the other hand you have to look at this a little more pragmatically I think. First is that its out there and its pretty much killing everyone that gets it, 83% for the rolling one year or so average. Second, we are overdue for a pandemic of some kind. You are right, it might not be flu. I dont think hookworms are going to take us out. Next is that regardless of what they say on the news you have to understand that they make the news. Anything that is good news is seized upon like a terrier on a rat. Nbarro has had to revisit his comments more than once. Next to lastly and here is one of the biggest is that they are spending one crapload of money on it. No one ponies on this planet the money to do anything other than to cull and compensate. I havent seen anything that they have done so far that remotely could be pointed to as being a thing that changed an outcome. Sheyit, it would be nice if they could.

Finally its the graphics and number of cases. They are continuing to grow in geographic area, cluster sizes, one or two medical types have become infected and all of these are conditions of pandemic by their own definitions. Why havent they called pan four? Politics and I can guarantee you its mostly China preventing this.

I personally fear for the US more than any other country as the ability to borrow is about gone and the Chinese hold our debt. They like the Japanese in the 80's are playing the old game, you can buy from us but not us from you. The difference here is that we would likely have to default as most countries would if panflu happens. Its a little off subject, but what would you do if money suddenly became worthless? That would apply to inbound oil and it would bring our economy to a screeching train wreck of a stop. I think this is the reason the countries of the world are in such a hell bent hurry to fund idiots in Indonesia that cull and compensate, then they use the money to buy more infected birds. Its a perspective of course and you could be right too. Wont know until this manifests itself as going or coming. My bet like Toms is that its coming. Everything I have seen is that its mutating towards us rather than away, sub-strains are appearing and each one is apparently acquiring human affinity.

Opposed to what this would do.... Give me a nuke any day.

By M. Randolph Kruger (not verified) on 15 Feb 2007 #permalink

"Everything I have seen is that its mutating towards us rather than away, sub-strains are appearing and each one is apparently acquiring human affinity."

Simple evolutionary biology says it aint so. If it's getting more human it must be getting less avian which would mean the demise of the strain no matter what what you might have read. Darwin has taught us that evolutionary change that does not benefit a organism will kill it. How does a mammalian change to an avian virus benefit it? The answer is it doesn't.

Shonda: That doesn't seem to be the case with either HIV or smallpox.

Shonda, hit me on memphisservices@bellsouth.net. I have the "End of Days" section graphics from the UN relating to major disasters, pandemics etc. We are way big overdue and the evidence is fairly strong that we will get a pandemic of somekind in short order. SAR's was a good example but it kind of mutated away. Statistically we are overdue for a pandemic, a 1918 pandemic, a smallpox type of epidemic as there was in the 7th and 8th centuries and later in the 17 and 18th. But we are HUGELY overdue for a Black Death type of pandemic such as the 1347 start in Constantinople. Interesting graph.

Lisa/Revere/Gracie/Tom would be more able to say of course, but the fact is that the graphics are continuing to show more geographical diversity, more cases, more fatalities. Most of the criteria for at least Pan 4 have been met including medical types getting it. Flamingly infectious? Not yet. Niman follows this like a hawk and he and Revere have both pointed out that this has been moving up the old respiratory tract. Once its infectious in the eyes, mouth, throat, nose then this will take off like a full blown bioweapon. I dont think anyone will argue that point unless they just like to argue. If you follow the phylogenetic trees that Niman puts out just about each time it mutates, someone else goes into a bag. Again, not flamingly infectious but the track has been for a while towards killing humans. I dont hear too much about massive bird kills anymore, only people. FAO/OIE I read every day and they have all sorts of goodies along with the WHO to make you worry. Endemically infected birds, poultry, cats, ferrets and each one is aiming their individual selves in our direction.

Of course hold onto your position. I fully support the fact that you could be right, but I dont think so. Me, I just pick up about another 3-5 a day on my email list for preparedness and send them out the list and hope to Revere's non existent God that this never happens.

By M. Randolph Kruger (not verified) on 16 Feb 2007 #permalink

How many different versions of H5N1 have they found now? How many different sequences?

Shonda, Nature is a lot more complex than you're making out.

So an avian virus is making new flavors that have also been infecting quite a variety of mammal species, for years, (including some mammals they aren't even testing enough yet); it is branching out, diversifying, not putting itself out of business.

Since it is contagious before symptoms it could stay 100% fatal as long as you're well for a few days; out with people, to give it a new home before you're "most flat".

Since it mutates so easily, what's to stop it doing whatever it wants?

Birds, poultry, farm animals, wild animals, (flies??) and, how many places are assuming any sickness in the population is what they "normally" get; many places to not have the resources to test for H5N1, or to sequence "seasonal" influenzas to see if they have picked up any bad bits of H5N1. What is going on? We don't even know.

We don't know because some governments won't tell, we don't know because some nations don't even have the infrastructure to tell.

Russia and Ukraine are having to close schools because of influenza; one place reported the number of cases in the 7 to 14 year olds is three times the level considered "epidemic".

Most African nations have so many people die every day of so many preventable causes, they aren't even going to be able to tell us in time if panflu breaks out.

By crfullmoon (not verified) on 17 Feb 2007 #permalink