Now to be serious about the flu virus for just a minute. The lead article in the November 24, 2005 issue of the New England Journal of Medicine is a must read for anyone who wants to make sense out of the hand-wringing in the media about the risk of the bird flu virus mutating into something that can spread from human to human.
The article is written by Dr. Robert Belshe, Professor in the Division of Infectious Diseases and Immunology at St. Louis University. It is titled The Origins of Pandemic Influenza – Lessons from the 1918 Virus. In the article, Dr. Belshe discusses the implications of the spectacular recent completion of the genetic sequencing of the 1918 influenza A virus by Taubenberger et. al reported in an article in the October 6, 2005 issue of Nature, and of a subsequent article in Science in which Tumpey et. al. used Taubenberger's sequence to recreate the complete 1918 virus.
The Taubenberger paper provides strong evidence that the 1918 (Spanish flu) virus was derived solely from a virus that originally infected birds, in contrast to its descendents, the 1957 (Asian flu) and 1968 (Hong Kong flu) viruses that arose when human and bird flu viruses infected the same person at the same time, allowing the genes to mix, a process known as reassortment. "Today, the descendents of this virus continue to cause the majority of influenza infections in humans."
I urge you to read the Belshe article, which contains an eye-opening schematic of the specific mechanisms by which the 1918 Spanish flu was transformed into the 1957 Asian flu, then the 1968 Hong Kong flu, as well as the genetic events which might be required in order to make the current H5N1 avian flu virus capable of adapting to humans.
My take-aways from the articles:
1. The bird flu is not new. Virtually all human flu cases since 1918 have been descendents of the 1918 flu virus, which was contracted from birds.
2. The good news. The genetic events that must take place to make the current bird flu capable of adapting to replicate among humans are extremely complex, therefore, extremely unlikely. More likely: a new pathogen that we are not even thinking about today.
3. The bad news. Pandemics happen. Plagues and pandemics have been a recurring story since the beginning of recorded history. It is highly improbable that we have seen the last one.
4. The other good news. As the ethologists write about, pathogens (the virus) and hosts (you and me) together form a system of mutual survival and interdependence. They refer to dynamic equilibrium in these systems as ESS, Evolutionary Stable States, in which hosts and pathogens are killing each other off at just the right rates to sustain current population parameters. In such systems, the adaptation of each makes the other stronger. It is nature's form of competition.
One of the most fascinating studies I have read was conducted by a group of biologists who compared the randon mutations of rat mitochondria (the little fuel processing organelles in each of our cells that have their own, much simpler DNA) during episodes of widespread plague and during normal periods. They found that mitochondrial DNA mutations occurred 3 times faster in the presence of virulent pathogens (during plagues) that during normal times.
I think this is precisely the system property that makes the US economy more robust and adaptable than most other major economies. As American business owners and managers can tell you, in the US competitors try to kill your business every day, forcing adaptation, cost cutting, rationalizing, restructuring, soul-searching and, ultimately, growth. Without the relentless attacks of pathogens (your competitors) none of this would happen.
My final, final, take-away from the articles is that we should give the viruses all the respect they deserve and devote sufficient resources to combat them over time. But we should not allow the presence of a virus to debilitate us with fear. Bird flu should be fought in the laboratories, not in press conferences.
There is one further cost of the current pandemic fear. We are neglecting the real problem. The probability that bird flu will become a human pandemic is very low. But the probability that the bird flu will cause massive hardships and hunger among the low-income farmers in China, Vietnam, and elsewhere in Asia is very real. In China, it is accepted practice to kill all poultry within 3 kilometers of a reported case of avian flu. Millions of poor farmers whose flocks are being destroyed are losing their only means of making a living, an event with potentially massive political and economic implications for everyone.