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Yesterday, Vietnam confirmed yet another human bird flu case.  This time, however, this case bears watching, because it could signal something far more disconcerting than just a single human case.

From the proMED report:

The Director of the Bac Kan provincial Health Department, Nong Quoc Chi, confirmed an A (H5N1)-infected case on [5 Apr 2010]. The patient, [male], 22, from Na Tao hamlet, Nhu Co commune, Cho Moi district, is currently in critical condition. He is being treated at the [National Institute of Tropical and Infectious Diseases]. The patient got sick on [30 Mar 2010] with symptoms of high fever and cough. He was admitted to Bac Kan provincial hospital, and then sent to the [National Institute of Tropical and Infectious Diseases] on [3 Apr 2010] where he tested positive for the lethal strain of A (H5N1) virus.

At present, 4 other people in Nhu Co commune show similar symptoms of high fever and cough. They are under quarantine and being treated at Bac Kan provincial hospital.

The patient in question was taken ill on the 30th of March, and then sent to Hanoi when his condition worsened. The four suspected human bird flu cases are currently in quarantine at the provincial hospital in the provincial capital of Bak Kan. (Or Bac Can, as shown on map at left).

There are many unanswered questions.  The most obvious of these is whether these four suspected cases are bird flu, or swine flu?

If these cases are indeed bird flu, has there been human-to-human chain transmission, or were these people all infected during the same timeframe by a single vector?  Were they all infected by sick poultry, or were they sickened by a human infection?

OK, let's assume these four people were all H1N1/swine flu infections.  That is not good news!  That would mean that, once again, bird flu and swine flu had "rubbed elbows" in rural Vietnam.  Search my Blogsite for the earlier known case, back in 2009. 

According to the Vietnamese Department of Preventive Medicine and the Environment, there are no outbreaks of H1N1 anywhere in Vietnam.  From VOA News:

No more A/H1N1 outbreaks in Vietnam

Over at Computerworld, I have just delivered my first blog in over six months!  And you thought I blogged slowly over here!

Anyway, I want you to go over there and read it, because I am not supposed to post their blog over here, and vice versa.  Here's the link: http://blogs.computerworld.com/15879/dont_write_off_h1n1_pandemic_yet

The CIDRAP study I mention in the blog was authored by Cecile Viboud, a research scientist at the National Institutes of Health's Fogarty International Center, and Lone Simonsen, research professor at the Department of Global Health, George Washington University, School of Public Health and Health Services, Washington, D.C.  Another co-author is Michael T. Osterholm, PhD, MPH, director of the University of Minnesota Center for Infectious Disease Research and Policy, and publisher of CIDRAP News.  Mike is also a good friend and I am danged glad to know him.  I have also mentioned Dr. Viboud's work on this Blogsite, particularly on the 1951 "Liverpool Flu" and her discovery of how deadly that epidemic was in the UK.

The recent CIDRAP study "sought to devise an 'apples to apples' way to compare pandemic and seasonal flu mortality. To estimate the age distribution of pandemic deaths, they relied mainly on a European study of 468 laboratory-confirmed pandemic deaths, published in August 2009. It showed that more than 85% of the deaths were in people younger than 60, with an overall mean age of 37.4, as compared with an estimated mean age of 76 in those who die of seasonal flu. (bold mine)

"The team then developed an estimate of pandemic deaths, given that only a fraction of cases and deaths are laboratory tested and that final statistics will not be available for another 2 to 3 years. This task involved comparing preliminary mortality data from the CDC's 122 Cities mortality surveillance system with final mortality data from the National Center for Health Statistics for 1999 through 2006. The team also used data on deaths in non-flu-season months to estimate the number of monthly deaths that would occur in the absence of flu.

"Using these variables and the 122 Cities data for April through December 2009, the researchers estimated the (US) pandemic death toll to be between 7,500 and 44,100. The lower number is based on deaths classified as due to pneumonia and influenza (P & I). The higher number, Viboud told CIDRAP News by e-mail, is an estimate of "excess all-cause mortality, which is more inclusive as it also takes into account excess deaths from all respiratory and cardiovascular diseases that are associated with influenza infection, but may not be reported as such."

"(Dr. Viboud) added that the 'excess all-cause mortality' approach has traditionally been used to measure the impact of seasonal epidemics and for the 1957 and 1968 pandemics, while the P&I approach has been used in assessing the 1918 pandemic. The team used both approaches to allow fair comparisons with past flu seasons, she said."

The study's results were revelatory.

• More than 85% of the H1N1(2009) deaths were in people younger than 60, with an overall mean age of 37.4, as compared with an estimated mean age of 76 in those who die of seasonal flu.
• the H1N1 (2009) pandemic, so far, has taken a toll of between 334,000 and 1,973,000 years of life lost (YLL) in the United States.
• The 1968 pandemic, with 86,000 deaths and victims averaging 62.2 years old, caused 1,693,000 Years of Life Lost (YLL).
• The 1957 pandemic, with 150,600 deaths and a mean age of 64.6,caused 2,698,000 YLL.
• The 1918 pandemic, with an estimated 1,272,300 deaths and a mean age of only 27.2, exacted a toll of 63,718,000 YLL.
• An average flu season dominated by influenza A/H3N2-which generally causes more severe epidemics than other strains-causes 47,800 deaths and 594,000 YLL, with a mean age of 75.7. (bold mine)

From the CIDRAP press release:

"Thus, the authors say, the lower end of their YLL estimate for the H1N1 pandemic is comparable to the estimate for an H3N2-dominated flu season, while the upper end is greater than that for the 1968 pandemic. Those impacts, of course, are dwarfed by that of the catastrophic 1918 pandemic.

"Based on US mortality surveillance data, we conclude that the YLL burden of the 2009 pandemic may in fact be as high as for the 1968 pandemic-but that at this time the assessment is still tentative," the report states. More waves of H1N1 cases are likely to come over the next few flu seasons, and later waves could be worse, it says."

Now for the commentary you have come to expect from this Blogsite:

H1N1 is not done infecting people, not by a long shot.  And as the CIDRAP study amply demonstrates, the impact of even this "light" pandemic on the future is significant.

Need context?  In the US, losing even 300,000 years if life in younger, productive stages will affect future payments to Social Security.  Medicare.  Federal, state and local taxes. Billions lost. Try factoring that into the budget deficit equations!  Not to mention the lost buying power of those persons due to the pandemic.

And of course, it goes without saying that the emotional burden of people having lost youthful loved ones to this disease is tremendous.  Watching someone get cut down in the prime of life -- especially someone previously described as healthy -- is a trauma no one would wish on anyone except Osama Bin Laden. 

Note something that not even I knew:  The 1957 and 1968 pandemics had a much older average age at death than has (so far) the 2009 H1N1 pandemic.  No doubt this is because we have the perspective of history and the separation of decades to view the cumulative effects of 1957 and 1968.  Since this H1N1 pandemic is far from over, its ultimate average age at death is yet to be determined. But at a shade over 37 years of age, the current age at death is second only to 1918's 27 years in terms of youthful mortality.

I believe it was my buddy John Barry (what a shameless name-dropper I am!) that said in his superior book The Great Influenza, that the average age at death in the United States from 1918-1919 dropped by ten full years as a direct result of both WWI and the 1918 Spanish Flu.

And let us not forget the lingering by-product of 1918's pandemic:  Encephalitis Lethargica.  That scourge stayed with America (and the world) until it mysteriously dropped from sight around 1930.  (Re)Watch "Awakenings" to recall that terrible ordeal.

I also want to crosswalk to a recent study that shows just how antigenically similar the 1918 and 2009 H1N1 viruses are.  From Reuters, via ChinaDaily.com:

WASHINGTON - The H1N1 swine flu virus may have been new to humanity in many ways but in one key feature its closest relative was the 1918 pandemic virus, researchers reported on Wednesday.

Their findings could point to better ways to design vaccines and help explain why the swine flu pandemic largely spared the elderly.

"This study defines an unexpected similarity between two pandemic-causing strains of influenza," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), said in a statement.

Two studies show an important structure called hemagglutinin is very similar in both the swine flu H1N1 and its distant cousin, the H1N1 virus that caused the 1918 pandemic. Hemagglutinin is used by viruses to infect cells and gives influenza viruses the "H" in their designations.

For one study, published in Science Translational Medicine, Chih-Jen Wei, Gary Nabel and colleagues at NIAID injected mice with a vaccine made using the 1918 influenza virus - which killed an estimated 40 million to 100 million people.

When they infected the mice with H1N1 swine flu, the vaccinated mice survived, while many unprotected mice died.

The reverse also worked - when they immunized mice using the 2009 H1N1 virus, and then infected them with the 1918 strain, the mice were protected.

"This is a surprising result," Nabel said. "We wouldn't have expected that cross-reactive antibodies would be generated against viruses separated by so many years."

The team also showed that as flu viruses circulate, they develop a kind of shield called a glycan that protects them from the body's immune system. That may allow them to become regular, seasonal visitors.

"It gives us a new understanding of how pandemic viruses evolve into seasonal strains, and, importantly, provides direction for developing vaccines to slow or prevent that transformation," Fauci said.

This type of experiment was performed in 2009, with similar results.  I believe Kawaoka did this type of work.  Webster may have done it also.  It reinforces the concern that one or two teeny little changes might really turn this virus into a nasty, nasty bug.

Policy makers, or persons who still labor under the false assumption that H1N1(2009) was a "false pandemic," would do well to examine the CIDRAP report.  Examine, and pray this virus does not mutate or evolve into anything more closely resembling its ancestor. Because it's uncomfortably close already.

As you know, I have been kvetching recently about the potential for a hybrid (or maybe "hybird," as I originally typed, in error but perhaps a Freudian slip?), avian/human flu virus to emerge from somewhere other than here.

Today, respected researcher Dr. Yoshihiro Kawaoka of the University of Wisconsin-Madison (left) has issued a paper where he postulates that such an occurrence is not only possible -- he has done it. 

Let's read the release and then talk.  From the University of Wisconsin-Madison press release:

VIRUS HYBRIDIZATION COULD CREATE PANDEMIC BIRD FLU

MADISON - Genetic interactions between avian H5N1 influenza and human seasonal influenza viruses have the potential to create hybrid strains combining the virulence of bird flu with the pandemic ability of H1N1, according to a new study.

In laboratory experiments in mice, a single gene segment from a human seasonal flu virus, H3N2, was able to convert the avian H5N1 virus into a highly pathogenic form. The findings are reported the week of Feb. 22 in the online early edition of the Proceedings of the National Academy of Sciences.

"Some hybrids between H5N1 virus and seasonal influenza viruses were more pathogenic than the original H5N1 viruses. That is worrisome," says Yoshihiro Kawaoka, a virologist at the University of Wisconsin-Madison and senior author of the new study.

The H5N1 bird flu virus has spread worldwide through bird populations and has caused 442 confirmed human cases and 262 deaths, according to the World Health Organization. To date, however, bird flu has not been able to spread effectively between people.

"H5N1 virus has never acquired the ability to transmit among humans, which is why we haven't had a pandemic. The worry is that the pandemic H1N1 virus may provide that nature in the background of this highly pathogenic H5N1 virus," says Kawaoka, a professor of pathobiological sciences at the UW-Madison School of Veterinary Medicine.

Two viruses infecting a single host cell can swap genetic material, or reassort, creating hybrid strains with characteristics of each parent virus.

Before the current study, hybrid viruses generated in lab studies had always been less virulent than parent strains. However, the new findings raise concerns that H5N1 and pandemic H1N1 viruses could reassort in individuals exposed to both viruses and generate an influenza strain that is both highly virulent and contagious.

The increased virulence seen in the new study seems to arise from one of the eight genes in the viral genome, called PB2, which is known to affect how well the bird flu virus grows in mammalian hosts, including humans. When tested in mice, the human virus version of PB2 swapped into H5N1 converted the avian virus to a highly pathogenic form.

The researchers say surveillance of viral populations is critical to monitor the potential emergence of highly pathogenic viral variants due to reassortment of avian and human influenza viruses. Their results, including identification of the PB2 segment as a key to enhanced virulence, offer information likely to be useful in the event of a pandemic caused by a hybrid avian-human influenza strain.

"With the new pandemic H1N1 virus, people sort of forgot about H5N1 avian influenza. But the reality is that H5N1 avian virus is still out there," Kawaoka says. "Our data suggests that it is possible there may be reassortment between H5 and pandemic H1N1 that can create a more pathogenic H5N1 virus."

The work was funded by the U.S. National Institutes of Health, the Japan Society for the Promotion of Science, the Ministry of Education, Culture, Sports, Science and Technology of Japan, and the Japan Science and Technology Agency. (bold mine)

Dr. Kawaoka's research is getting a lot of attention, including a recent grant from the Bill and Melinda Gates Foundation.  What is so interesting about Dr. Kawaoka's recent experiments is that he targeted PB2, the segment which few know enough about to be decisive.  Dr. Kawaoka and his research team have taken a human PB2 gene segment and spliced it to H5N1 bird flu.  The result is a more lethal and even more virulent virus than the parent H5N1 strain!

Dr. Kawaoka and his staff have now, and pretty conclusively, named PB2 as the gene segment responsible for lethality in humans.  In prepping for this blog, I stumbled across a blogsite by the name of Monotreme's Blog, and how I never saw it before now is a mystery to me.  Anyway, this blog has an interesting confirmation of Kawaoka's discovery.  But it turns things in a different direction than an avian/swine hybrid doomsday virus.  From Monotreme's Blog entry of December 2, 2009:

The PB2 gene is reported to be key in the adaptation of a virus that infects birds to one that infects humans. In particular, it has been reported that the amino acid at position 627 is critical for this adaptation (Van Hoeven et al. 2009). Viruses that infect birds typically have a glutamic acid (E) in this position. Flu A viruses that are fully adapted to humans usually have a lysine (K) at this position. This same position in PB2 appears to be key in determining the lethality of flu viruses (Hatta et al. 2001). In the 1918 pandemic and H5N1 viruses, a lysine in this position is associated with a higher level of lethality. The presence of a lysine at position 627 appears to permit flu viruses to replicate in both the lungs and nose and thus spread more easily from person to person.

It is possible, perhaps likely, that as pandemic H1N1 adapts to humans, a mutation will occur that will create a lysine in position 627 in this virus. If so, will the virus become more virulent? At this point, it is difficult to say. On the one hand, “seasonal” flu viruses that are not considered particularly lethal have a lysine at position 627. On the other hand, a change from glutamic acid, when the virus is infecting birds, to a lysine, when the virus is starts to infect humans, is associated with much greater virulence. How to reconcile these apparently contradictory facts? It may be that the change to a lysine is initially associated much greater virulence due to interactions with other proteins. As the virus moves through the human population immune responses are triggered. Thus, a year or two after a pandemic begins, the virus comes under selection to escape immune system detection. This selection may result in the preferential propagation of new versions of other proteins which no longer interact with PB2 to create a more lethal virus. In this scenario, a mutation at position 627 from gluatamic acid to lysine will initially create a more lethal virus, but, as the virus is “tamed” by the immune system selection, this mutation will utlimately be insufficient to sustain a high degree of lethality.

Given that human-adapted flu A viruses tend to have a lysine at position 627, it seems likely that the new pandemic H1N1 will eventually lose its “avian” glutamic acid and acquire a lysine at this position. There have already been sporadic instances of this. If/when this occurs in a strain that spreads widely, it would not be surprising if it becomes more lethal.

Kawaoka's research has taken Monotreme's (and others') speculation and turned it into fact.  

Monotreme offers a theory that immune responses in humans will ultimately steer this lysine-altered virus toward a less lethal path in order for it to evade antibody detection and eradication.  But how long will that process take, and how many lives would be impacted by the virus in the meantime, are only known to God.

In the meantime, bird flu continues to buck the tradition of flu viruses during a pandemic.  this virus refuses to go away.  Just today, comes word of two more Egyptians struck down with H5N1 bird flu.

Now I am going to make a statement, and I want you to read it and absorb it.

There have been more Egyptians hit by H5N1 bird flu thus far in 2010 than there are Americans who have tested positive for H1N1 or H3N2 seasonal influenza.

Bird flu continues to spread again, in defiance of tradition and in defiance of all governments' attempts to eradicate it.  As the H1N1v pandemic continues to strike and spread in Asia, the potential for dual infection with H5 and H1 simultaneously increases.  How many cross-infections does it take to achieve some sort of viral critical mass?

Only one. 

The Centers for Disease Control and Prevention issued an update regarding swine flu, or H1N1v, today.  The numbers draw me to draw up an interesting set of suppositions.  I thought it would be of importance to parse these numbers, analyze them and draw some observations and conclusions from them.

First, as everyone wants to know, just how many people in this country have died from H1N1v?  Well, the CDC's answer to that would make Harry Truman cuss. 

CDC Estimates of 2009 H1N1 Cases and Related Hospitalizations and Deaths from April 2009 - January 16, 2010, By Age Group

OK class, let's follow along.  And let's just look at that last row.  The CDC states that anywhere from 8,330 to 17,160 people have died in America from H1N1v or its complications.  Using an algorithm to determine the midpoint (and I am certain that statisticians much, much smarter than I have alloted for the severity of the virus being greater in Wave 2 than in Wave 1), the midpoint is pegged at 11,690.  That is an increase of 530 Americans since the previous report in mid-January. 

Everyone wants an exact number, which of course is both meaningless and impossible to produce.  But I want to stress that these are the same algotithms that produce the vaunted, take-it-to-the-bank figure the global press uses to determine seasonal flu deaths.  Does this sound familiar? 

"Annually, some 36,000 Americans die each year from seasonal flu."

That mantra is repeated over and over and over again.  Repeated so much so, in fact, that it has become a pillar of certainty.  Some recently have dared to debunk that wisdom, saying that, in fact, the number may be closer to 20,000.  But it matters not.  the number 36,000 is etched into the National Consciousness forever.

Good!  Let's use that figure and compare apples to apples. 

The CDC states that 90% of all seasonal flu deaths are persons ages 65 and older.  But in this current pandemic, just over 87% of the deaths are of persons aged 64 and younger. Only 12.6% of the deaths are of persons 65 and older.  A full 10.5% of the deaths are pediatric (ages 0-17).

For those who believe this H1N1v to be a "false pandemic," your argument just got shot out of your backsides.  In a traditional flu season, fewer than 1% of the deaths are of children ages 0 to 17.  In fact, that number is fewer than one-half of one percent.  So the number of children who have died from H1N1v is seven times the yearly average.  Sorry, debunkers.  You don't generate those kind of numbers with seasonal flu, no matter how bad it is.  Only a bona-fide pandemic generates that type of data.  And that kind of death.  Checkmate. Game, set and match.

Enough b**ch-slapping of the "false pandemic" crowd.  Let's get back to the numbers at hand.  And let's also look at what this virus might eventually do, according to Dr. John Oxford.  It's a long road, just follow my logic.

Eventually, based on previous pandemic flu virus behavior, this flu virus is going to mutate.  There is already some evidence of two key amino acid substitutions in the receptor binding domain, popping up in multiple areas of the planet pretty much simultaneously.  (Receptor binding domain means the way the virus latches on to cells in the epithelial tract, for those of you in Rio Linda).  

As influenza is wont to do, it produces thousands of mutated offspring, and one particular offspring seems to be at the very least, trying to take root in several locations all over the world.  If this mutation takes hold and replaces the current H1N1 strain, it will pose a serious risk of producing additional sick and additional dead, based on the fact most of the amino acid changes were detected in the lungs of dead victims.  But whether or not this mutation holds is simply speculation and we will not know it unless and until it manifests itself in numbers large enough to be detected.

What we do not know yet is what form and substance H1N1v will take to alter its proclivity toward younger hosts and start zeroing in on the elderly.  But we can be assured enough to bet that once again, based on prior pandemic virus behavior, and as Sam Cooke famously sang, A Change is Gonna Come. 

But wait, you ask. Just today,  the WHO today released a report that said, in essence, that H1N1v is slowing down throughout most of the world.  The notable exceptions are Asia, eastern Europe, and certain African nations.  In Australia, the virus has almost disappeared -- and isn't that not supposed to happen with a pandemic strain?

A flu virus slows down when one or more of several things happen.  the virus slows down when climate changes in a way unfavorable to the virus (high temperatures with high humidity, for example). This explains why, in Australia and Brazil, for instance, the virus is laying very low.

Another reason why the virus may slow down is that it has burned through its largest pool of available hosts.  At that point, the virus has three directions it can go.  It can die out, it can be overtaken by another flu strain, or it can evolve around the problem.

Most pandemic flu strains choose the latter course and evolve, or mutate, or whatever you want to call it.  Publish or perish?  With viruses, it is evolve or perish.  This has been repeated over and over and over again too many times to count.  This is how we get seasonal flu.  This is why we get flu shots annually, instead of once or twice.  Why in the world anyone would expect this virus to simply lay down and die without fighting is contrary to every known rule (or supposition) regarding the behavior of influenza.

So this virus, when faced with a loss of available hosts, will probably do what the overwhelming majority of pandemic and post-pandemic viruses will do:  It will evolve and seek other hosts. 

So we've got nearly 12,000 dead in the USA from swine flu, and only 12.6% are seasoned citizens.  Now what happens when this virus changes its genetic structure and starts infecting those seniors?

We get 36,000 dead annually. 

Add the potential for the addition or retention of those two amino acid changes, and we get a virus that quite possibly will evolve beyond the original vaccine target.  Or maybe not.  The smart play would be for anyone not yet vaccinated to hurry up and get that dang shot!  And for parents of kids under 9 to get that H1N1v booster shot.  Remember, ages 9 and under need two jabs.

Let's do the math.  Take 12,000 dead, and add 36,000 to it.  That is 48,000 people.  That is more than died in the 1968 pandemic and is about the same CFR as occurred in 1968, adjusting for population.  But if this virus gets any more lethal, and we could be looking at numbers comparable to the 1957 pandemic.

Quoting the the UK's Guardian, The last big flu outbreak in Britain occurred in 1999/2000, when 22,000 people died, which is 10 times the average for a winter flu season.  Professor John Oxford is one of the oldest and most respected flu researchers on the planet, and is habitually quoted on this Blogsite.  In late December 2009, Professor Oxford famously said (thanks to Crof for the link): 

My greatest fear is that the virus will mutate next year, to enable it to infect older people. If it does, then the death rate next year will be much worse than this, perhaps even as high as the winter of 1999-2000. 

Remember that between a third and a half of all people who have ended up in intensive care with swine flu were previously completely well; they weren't asthmatics or on chemotherapy. While the pandemic has been fairly mild here, I think it will kill off for ever the notion (among doctors and the public alike) around influenza that "Oh, it's only flu". 

My last blog focused on the return of H5N1 avian influenza in humans in 2009.  Just scroll down to read it... I'll wait.

OK, welcome back.  What is happening is a veritable explosion of bird flu across Asia and the Middle East in 2010.  We have over 400 residents of West Bengal (India) under Tamiflu blankets; human cases seemingly every third day in Egypt, and at one point we had three confirmed cases in one day; and a quite sudden acceleration of H5N1 in poultry and wild birds across most of southeast Asia. 

Now Indonesia, a nation which has thankfully turned away from insanity with the appointment of a new health minister. is back in the timely reporting category.  Hey, anything was better than the last two years under Supari!  They could have had a zombie epidemic and the rest of the world could have been blissfully unaware -- until the undead came down Broadway.  And speaking of zombies -- where the Sam Hill is that World War Z movie?  Brad Pitt and Plan B, don't make me come down there and read you the Zombie Riot Act.  Why do you think Zombieland was such a financial success?   And a bit of movie trivia -- Zombieland's central character (right) was named Tallahassee, by the way.

But I digress.  Anyway, Indonesia has now reported two confirmed human H5N1 cases.  One case is in West Java, and one is in Jakarta.  Regrettably, the West Java case -- a 25-year old of unknown gender -- died.  I am sure that if you go to www.flutrackers.com, you will find plenty of stories about the deaths. 

And just this morning, news of a third Indonesian bird flu patient arrives via proMED.  This patient, a woman in Lampung, accompanies a huge die-off of birds in the province.

While this is taking place, the Western press is reporting about the roasting of public health officials over regarding what some misguided souls proclaim to be a "false pandemic" of H1N1v.  As the public health officers of the civilized world circle the wagons in the West, swine flu continues to insinuate itself throughout Asia.  Ans as it does what the flu does, it will absolutely have multiple opportunities to rub elbows with bird flu in towns and villages.  It has already had multiple opportunities with each and every confirmed human H5N1 case since April of 2009. 

Everyone is asking him/herself, "What virus was shed by those who are testing positive for bird flu?  Who might have walked into a cloud of H5N1 particles expunged by someone?  And what if that person, in turn, also acquires H1N1v swine flu?  Deep in the lungs of those dual-flu victims, what terrible reassortment experiments might be churning?  And what is the form and substance of that mutation, if it survives?"

Wait, you ask.  Why should swine flu mix with bird flu?  Recall that swine flu is only one-third swine.  It is also one-third human, and one-third avian.  Look at the number of flocks of turkeys all over the world that have acquired swine flu.  (interesting that I can only recall turkey flocks having acquired H1N1v).

For these flocks to have acquired a human strain of flu surely must tell us that H1N1v retains enough of an avian genetic footprint that direct infection from humans to birds is not just possible -- it has happened.  Numerous times.

Follow my logic here.  If birds can catch swine flu from humans, then it means swine flu retains enough of its bird ancestry that reassortment with bird flu is absolutely possible.  All it takes is enough exposure, in enough hosts, all over the world, to cook a strain that can both infect humans and kill in greater numbers than swine flu.

Sure, the swine flu pandemic was not what we were fearing.  But let's finish the sentence.

The swine flu pandemic was not what we were fearing -- yet.  We have a long, long way to go.