I tend to read a lot of scientific books, and usually they're enlightening, often fascinating, but all too frequently the prose leaves something to be desired. The author who can bring a very specialized field alive for the non-specialist is truly one to be savored, hence this review. Ryan's writing, when he describes the investigative process of discovering and isolating a new virus is sharp, well paced, and as engaging as the best detective fiction.
My other frequent gripe with scientific books for the non-scientist is their treatment of the technical details. Often scientific authors are forced to employ a very specialized vocabulary, at which point they generally either carefully gloss every term for the layman, dragging the narrative into swamps of background, or they neglect to explain anything at all, leaving us wandering in a wasteland of latinate mystery. Sometimes they choose the other extreme and avoid technical details at all cost, leaving the intelligent non-specialist feeling like they don't know any more about the topic than they did when they started.
Ryan again manages to thread this needle, employing just as much technical terminology as he needs to, and explaining some of the more complex processes, such as the genetic manipulations needed to clone samples of viruses, without either talking down to the reader, or assuming that his audience is composed entirely of PhD.s.
But enough of that. The real meat of this book is two fold. First, it is an enlightening primer on the current (as of 1997) state of global epidemiology, and an overview of the biggest current threats to public health, especially in virology. Ryan describes the first outbreaks of such emerging viruses as the sin nombre Hantavirus in the Southwestern US, Ebola Zaire in Africa, and HIV, in Africa and the US. He follows epidemiologists as they attempt to determine the causes of mystery disease outbreaks, isolate the viruses responsible, and discover the virus's natural reservoir in the local ecology. For anyone who enjoyed The Hot Zone, the real life stories presented here, are even more interesting.
Finally, Ryan presents his theory on where these brand-new viruses are coming from, and why they are often so disastrously fatal to humans. The "standard theory" is that since we know that there are viruses specific to nearly every species of life on earth, and we know viruses often mutate very rapidly, sometimes a virus from one species will happen to mutate in such a way as to be infectious, and even fatal to another species, such as humans.
But Ryan's theory is much more interesting, and, from the point of view of a confessed non-biologist, much more probable.
He tells the story of a certain type of ant, which builds its nests only around the base of a species of rattan cane that grows in Borneo. The ant colonies derive their sustenance from the sap of the cane, and in return, they will attack and sting any animal that attempts to eat their home plant. This is a classic example of symbiosis, where two different species evolve into a relationship where the behaviors of one perfectly complement the behaviors of the other.
Ryan postulates that viruses might be engaged in very much the same practice, at the level of the genome. Viruses are extremely dependent on their host species, since they cannot reproduce without using the genetic and biological machinery of the host. Most species harbor many strains of virus which infect them endemically, but do little or no harm to their host. The most common pattern in emerging virus epidemics is that of a virus from a local species suddenly "jumping" from it's natural host into humans, and proving to be disastrously fatal once past human immunological defenses.
This is the quandary: why would viruses select for aggressive lethality, when they themselves can't survive without a host organism? Many scientists dismiss it as chance mutation, but Ryan suggests that perhaps it's necessary to look at the bigger picture to understand this pattern. What if the virus isn't trying to establish a new host territory, but instead, is trying to remove a threat to its existing host species?
Another common pattern, seen for example in the first outbreaks of the sin nombre Hantavirus, is that viral epidemics are preceded by an unusual increase in the local population of their native "reservoir" species. Perhaps, argues Ryan, with the increased competition for resources between a virus's host species and another local species, the virus is acting as a defense mechanism for its current host, selecting for lethality to wipe out the competition, and preserve it's existing host species.
Obviously, he doesn't wish to ascribe intentionality to a virus. Clearly they don't "think" or "plan" to do this. But the effect is the same, since their behavior will likely be selected by maximum benefit to the species. Hence, Ryan neatly unifies both the symbiotic and the evolutionary strains of ecological thought, in a kind of evolutionary symbiosis between virus and host.
Along with this theory, Ryan proposes that humanity is going to have to start taking a much more holistic view of what our actions are doing to the world as a whole. Often, it seems, we are our own worst enemies, provoking new plague outbreaks by encroaching upon long-pristine territory. He feels that, if we continue upon our current course of deforestation and general exploitation of resources, it is only a matter of time before one of the emerging viruses combines both the dreadful infectiousness and lethality of, say, Ebola, with the efficient infective vector of the flu. An Ebola spread by airborne aerosol would be likely the worst disaster humanity has ever experienced, killing potentially 90% of humanity worldwide.
How can we avoid this doomsday scenario, this "Virus X"? Ryan argues convincingly that we must learn more about how viruses work, we must improve our preparedness for emerging pandemics, and most of all, that we must stop the pell-mell environmental exploitation that has been the hallmark of humanity since the industrial revolution, and before.
Overall, this was one of the best scientific books I have read in a long while, and it is highly recommended to anyone who'd like to learn more about virology, or epidemiology, or anyone who just likes a cracking good science yarn.
Virus X: Tracking the new killer plagues is 382 pages, plus footnotes and index.
It is published by Back Bay Books,
and is available from Amazon.com and Fatbrain.com.