Monday, February 23, 2009

The Viruses Just Let Us Live Here... far.

I've been sick the last couple of weeks, so what do I choose for reading material? A book about smallpox, anthrax, and bioterrorism, of course. Richard Preston has a way of turning a true story about scientists, viruses, and horrible diseases into a compelling page turner. I read his 1994 book The Hot Zone a couple of years back. Great read. That was about ebola, which is a horrifying disease but one that is not especially effective in keeping itself going in a human population, mainly because it kills its hosts too quickly.

The Demon in the Freezer is mostly about smallpox. Smallpox (the virus itself is called variola) is a much "smarter" virus. It is one of many "poxviruses" that occur in nature (cowpox, monkeypox, mousepox, even various insect poxviruses). Smallpox only infects humans. It is very lethal, but it also has evolved excellent "strategies" for spreading itself through human populations once those populations reach a certain critical size and density (it could be called the first urban virus). Smallpox has killed untold millions of people and is considered by many to be the worst disease in human history.

But then in 1979, it was gone. "The Eradication" was one of the greatest feats of modern science, medicine, and public health, and Preston tells the story well. There were a lot of dedicated people, and in spite of many setbacks, through a sophisticated containment strategy involving many, many vaccinations, variola was eliminated from the human population in just a few years, with only two authorized supplies of the virus retained for possible research, one in the US and one in (now) Russia.

Or so we were told. In fact it is now known that the Soviets kept many strains of variola in many places and even did research to "weaponize" the virus so it could be launched on missiles with multiple warheads that could parachute down and spread an aerosol of the virus over a wide area. They produced at least 20 tons of weaponized smallpox in the 1980's (enough to kill trillions of people). No one knows what happened to all that stuff or what countries or groups may have some of it now. Scary? Yes, but not the scariest.

The scariest thing is that poxviruses are among the easiest to genetically engineer. Preston tells of an Australian research team that engineered a mousepox virus by introducing a gene from the mouse's immune system into the virus's genome. This was part of a rodent control research project, and in their tests, the proteins produced by the introduced mouse gene seemed to confuse the immune system of the test mice. While natural mousepox is not very lethal in resistant mice, the engineered virus killed 100% of the non-vaccinated test mice, and 60% of the vaccinated test mice! Could human smallpox be similarly engineered with a human immune system gene? Pretty easily. It probably already has been done somewhere. Would it have the same effect on smallpox lethality even for immunized subjects? No one really knows.

Preston also talks a lot about the anthrax attacks of fall 2001, mainly to show the practical difficulties of dealing with deliberate attacks with bioweapons (there are difficulties for both the attackers and the defenders). Smallpox is a much "better" weapon than anthrax, even if it is not genetically engineered. And the fact is that while smallpox has been eliminated "from the wild," it has not been eliminated from the world. We don't really know who has it.

So for now, variola and its various virus friends are letting us live here on Earth. But as Preston says at the end of The Demon in the Freezer, variola is one clever little virus and it is not out of the game yet:
The virus's last strategy for survival was to bewitch its host and become a source of power. We could eradicate smallpox from nature, but we could not uproot the virus from the human heart.

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