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03/07/2005

Nothing to sneeze at

1918_influenza_epidemic

I've been laid up with a bout of the grippe, so I've fallen behind the news curve. But this Reuters story from last month caught my eye:

The threat of a biological terrorist strike by al Qaeda is very real but the world is still not prepared, the head of Interpol said.

Ronald Noble said governments, police and security services were more organized than ever before but he warned it would be wrong to assume the threat from Osama bin Laden's group, blamed for the Sept. 11 attacks on the United States, had eased.

"The terrorist threat is as real today as in 2001 when September 11 occurred," Noble said in an interview with the BBC late on Tuesday.

"The number of terrorist attacks that have occurred around the world and the evidence that has been seized revealing the kind of planning that al Qaeda has done in the area of biological weapons or chemical weapons … is enough evidence for me to be concerned about it.…"

"Anyone who is honest about this has to admit that if al Qaeda launches a spectacular biological attack which could cause contagious disease to be spread, no entity in the world is prepared for it," Noble said.

This detailed analysis from Recombinomics is even more sobering:

If pandemic flu is the contagious disease of choice, selection of WSN/33 at this time would offer some advantages. It is already transmissible from human-to-human, has been shown to be lethal in mice, has mutations in NA and PB2 that increase lethality, is widely available, and could be used without genetic manipulation.

As has been seen in Korea, introduction of the agent into pigs would allow it to spread almost undetected. Verification of its spread (or existence) has proven to be exceedingly difficult.  Movement from swine to humans has not been reported and all reported isolates are missing the PB2 mutation. This may be due to a survival selection offered by recombining or reassorting with prevalent H9N2 subtypes. Most of the swine isolates have an avian PB2, but even the isolates that have half of a human PB2 have the 3' half of the human gene replaced with avian sequences. Thus, the results from the Korean swine may indicate that starting with a very lethal virus has disadvantages in that a less lethal virus will emerge virtually undetected.

A second choice would be the H5N1 currently causing the high case fatality rate in Vietnam, Thailand, and Cambodia. This version would be even more available, since it is excreted in large amounts by asymptomatic ducks, and is present in multiple organs in fatal infections. Although human-to-human transmission of H5N1 is limited, infecting a few international travelers would generate worldwide panic if these passengers became ill outside of areas with indigenous H5N1.  Use of infected currency as a vector for transmission has been widely discussed.

A third approach would involve genetic manipulation. Creating an efficiently transmitted H5N1 would be relatively easy. Swapping a human receptor binding domain from a human flu virus into an H5 backbone would improve transmission efficiency and such an agent would quickly disseminate worldwide. Of course such an agent would be hard to control, and most unvaccinated people would be at risk. Since influenza evolves via recombination, implementation of an efficient laboratiry strain might be eclipsed by a natural version, and there would be uncertainty over the origins of such an agent.

Thus, like WSN/33 in Korean swine, taking credit for such a biologic attack may be difficult, since most countries appear to be unable to even determine if such an attack has happened.

[A flu primer that can help you decipher terms like NA and PB2 can be found here. It'll definintely make you the envy of your non-medical-expert friends.]

The current avian flu strain (H5N1) that has been ravaging Vietnam—should it mutate (or be deliberately weaponized) into a form that's easily transmitted person to person—could produce results as devastating as the 1918 influenza pandemic that killed  as many as 100 million people around the world, 600,000 of them in the United States.

In The Great Influenza—his definitive history of the 1918 epidemic—John Barry cheerfully writes, "A weaponized influenza virus could be the equivalent of a worldwide nuclear holocaust."

Laurie Garrett describes the near-miss of just such a holocaust that occurred back in December:

Shortly before Christmas, some genetic data was—as a matter of routine—posted with GenBank, a mammoth, publicly accessible computer repository located at Los Alamos National Laboratory in New Mexico. No special phone calls were made, no alarms sounded. But the GenBank posting looked like the genetic code for a new, manmade killer influenza that was infecting pigs in South Korea. Fingers seemed to point to Pyongyang.

Before you have a heart attack, let me assure you that, two months later, it looks like the nightmare of weaponized super-flu did not happen this time. But the scenario that played out is probably pretty close to what might unfold in a genuine bioterrorism incident, and it reveals critical weaknesses in our global security system—or lack thereof.

If your nerves aren't sufficiently jangled, here's the latest word on the H5N1 avian flu virus from the CDC, a Vietnam update from the WHO and a Q & A on the subject from The Wall Street Journal (via The Pittsburgh Post-Gazette).

Recombinomics has further disturbing thoughts here and here. This post at Redstate.org is also worth a look.

Stay tuned.

Posted by Rodger on March 7, 2005 at 11:04 PM | Permalink

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