H1N1 + H5N1 = ?

Until the surprise outbreak of what the CDC is now calling "novel influenza A (H1N1)" a couple of weeks ago, if you had asked which strain of flu virus was most likely to cause the next pandemic, most experts (and even news-consuming lay people) would have told you the same thing: H5N1

The H5N1 flu virus is either a panzootic in birds (a panzootic is just like a pandemic, but for animals), and has shown the ability to infect a number of other species in a more limited way, including the friendly neighborhood tom cat... and yes, the occasional human.

And we've been quite lucky that it's only been the occasional human, because of the 421 confirmed cases we've seen over the years, 257 have been fatal.  That's a case fatality rate (CFR) of just over 61%.  It's a mean and nasty bug.

So, at this moment when much of the world is learning about recombinant flu viruses for the first time, it's not surprising that a lot of people (or at least a lot of the people who post comments in blogs and bulletin boards) are wondering whether the H1N1 virus and the H5N1 virus could combine to create a virus far more lethal than H1N1 and far more capable of human-to-human transmission than the H5N1 virus.

The bad news is that, yes, it's possible.

The good news is that it's not terribly probable, because -while the H5N1 virus is capable of infecting humans and a broad range of animals- for the most part it continues to be a disease of birds.  It typically doesn't reproduce very well in pigs at all, and humans seem to be a dead-end host for the virus so far.

The Novel Influenza A/H1N1 virus, of course, is mostly a disease of humans (though it is apparently willing to move back in with the pigs too).

In an interview with Science Insider, virologist Yi Guan of SARS fame shared his thoughts on the possibility:

Discussing the our inability to predict whether the H1N1 virus will become more virulent....

Q: It depends on further mutations?

Y.G.: It depends on mutations and whether the virus further reassorts with other viruses—like H5N1. That could be a super nightmare for the whole world.

Q: You’re talking about the Armageddon virus?

Y.G.: The chance is very, very low that these two viruses will mix together, but we cannot rule out the possibility. Now, H5N1 is in more than 60 countries. It’s a panzootic, present everywhere except North America.

Q: If the nightmare comes true?

Y.G.: If that happens, I will retire immediately and lock myself in the P3 lab. H5N1 kills half the people it infects. Even if you inject yourself with a vaccine, it may be too late. Maybe in just a couple hours it takes your life.

Sounds pretty scary, and it could be... but you'll recall that he said the chance of it happening is very, very low.  

This is a good illustration of the difference between a hazard (something that can cause harm) and a risk (the likelihood of that harm actually occurring).  

An H5N1/H1N1 recombinant virus represents a serious hazard, but the risk of it actually happening is thankfully rather low.

That doesn't mean we can afford to take our eyes off the ball, however.  The H5N1 virus is no less of a threat today than it was before the H1N1 outbreak began, and we ignore it at our peril.  President Obama says that the President of the United States needs to be able to walk and chew gum at the same time, and he's right.  Here's to hoping the global public health preparedness community can do the same.

Bogus: Bioweapon claims for H1N1 Swine Flu

Some segments of the blogosphere are all atwitter (pun intended) with the theory that the H1N1 Swine Flu must be the work of some nefarious group of bioengineers because the virus contains segments from 4 different progenitor viruses --2 different swine flu viruses, an avian flu virus and a human flu virus.  Some even seem to imply that US government researchers working on the 1918 pandemic flu virus (which was also an H1N1 virus, though very different) might have been involved in weaponizing it.

Much of this seems to be driven by a story written by Wayne Madsen of Online Journal:

It turns up all over the place, at PrisonPlanet.com, Know4Life, InTheseNewTimes, and elsewhere.

Jeff Denmark at Drudge Retort quotes the article:

"According to two mainstream media journalists, one in Mexico City and the other in Jakarta, who spoke to WMR on background, they are convinced that the current outbreak of a new strain of swine flu in Mexico and some parts of the United States is the result of the introduction of a human-engineered pathogen that could result in a widespread global pandemic, with potentially catastrophic consequences for domestic and international travel and commerce." 

And goes on to say: "WMR has been informed that the CDC and U.S. Army dug up the body of an Inuit woman who died in 1918... from an outbreak of Spanish flu. . . . . WMR has been told the genetic material recovered by the U.S. government from the corpse of the Inuit woman provided the basis for the development of the H5N1, or bird (avian), flu strain at the U.S. Army Medical Institute of Infectious Diseases (USAMRIID) laboratory at Fort Detrick, Maryland, the point of origin for the Ames strain of anthrax used in the 2001 bio-war attacks against the U.S. Congress and the media."

This is, as they say in Jolly Olde England, complete rubbish.

"How, then" you may ask "did a brand new virus that's made up of four different viruses suddenly spring into being and spread all over the world? Doesn't it have to be the result of bioengineering?"  

...Actually, no.

This is exactly the sort of thing we've been expecting for years.  

If more than one strain of flu virus infects the same cell, the two strains can mix up their genes, leading to what is called a recombinant virus.  That simply means that the genes from the two (or more) viruses have recombined to create a new strain.  In effect, it's a lot like sexual reproduction in humans; parents mix up their genes with the result that a child might have her mother's hair and her father's eyes.

This recombination happens especially easily in pigs, because they can be infected by swine flu viruses, avian flu viruses and --you guessed it-- human flu viruses.  The pig as a "mixing vessel" scenario is something we've long known to be a threat when it comes to pandemic flu.  In fact, this is believed to be what caused the last two pandemics, in 1957 and 1968, as this figure illustrates.

This is perfectly natural and expected.  That doesn't make it good, of course, but there's no hidden conspiracy behind it.  The virus arose naturally and the epidemiological evidence seems to show pretty clearly that it's spread so quickly because of air travel --something else we knew to expect-- not because it's being used as some kind of very inefficient bioweapon.

We humans are all on the same side on this one.