Monday, December 05, 2005

The Globalization of Disease

In recent years there has been much alarm over one newly emergent virus after another – Ebola, Marburg, SARS and now avian flu. The fear arises because these diseases are extremely dangerous and because, it is thought, modern transportation patterns threaten to transmit the virus around the world at lightning speed. I suspect these fears are exaggerated.

With an infectious disease one can best think about the danger (for a given level of intrinsic deadliness) by considering which of two sets of factors is more powerful: those that dampen the disease’s spread, and those that accelerate it. Much of the more panicky coverage has emphasized the latter and not thought much about the former. This is not necessarily a bad thing; we want people at places like the CDC to be thinking about worst-case scenarios. But for the rest of us thinking about how much to worry about such things, and whether we should change much of our behavior, some perspective is in order.

The most prominent factor promoting acceleration is global travel. Someone can get sick with a new virus produced in the toxic brew of highly dense populations and close human-animal contact that prevails in East Asia or Africa and be in New York or London within hours. Indeed, this was the way SARS spread so rapidly from China to Canada and the U.S. But the SARS lesson is actually striking for what did not happen. The disease was frightening when it first came out, and as it spread from Asia to Toronto. (As an aside, Mark Steyn in a column requiring free registration at the Western Standard, makes the interesting if debatable point that the spread of single-payer health care systems is an accelerating factor. He claims that the inattention to hygiene plaguing Canadian state care as opposed to profit-driven American health care made the disease much worse in the former.) If one compares the ease of global travel and the extent to which people from all parts of the world mingle now compared to the time of the 1918-1921 Spanish flu, perhaps the most devastating epidemic of the modern era, it is clear that the forces promoting contagion are considerably greater. And yet SARS did not turn into that, despite many contemporaneous predictions that it would.

And that is because the forces promoting dampening are so strong. The ability to detect the disease through quick and easy lab tests is much greater, so that those who might have been exposed can be tested (perhaps because they are ordered to, and governments giving orders is also a process that is much more efficient now) even if they are not symptomatic. The ability of the pharmaceutical industry to capitalize on eighty-plus years of accumulated knowledge, plus any new knowledge they and the biomedical establishment generate in the course of responding to new diseases, is incomparably greater. This combination of scientists and salesman, public and private is a far more formidable force than it was in previous epidemics. The capacity to develop medicines and vaccines might then be correspondingly greater. And globalization probably helps much more than it hurts – global communications technology and competition among information-providing firms allow (despite government attempts to minimize the danger in societies such as China) much better monitoring of the spread of the disease, which in turn feeds back to public-health authorities.

The sum of the effects on both sides of the ledger is likely to strongly favor containment, as has been the case for all the other potentially catastrophic viral innovations mentioned above. The obvious counter-example is HIV, which was first identified in the early 1980s and has gone on to kill millions. But that disease has several factors promoting acceleration that do not apply to an airborne pathogen. Because it is a venereal and needle-borne disease, being spread through the most intimate types of behavior, the ability of public-health authorities to get truthful answers and monitor disease spread is much more difficult. No sense of shame attaches to the behavior leading to acquisition of influenza in most places (although the material consequences of quarantine might be substantial). This combined with the rapid onset of severe symptoms means that victims, often because they go there themselves, become known to public-health authorities soon after getting ill, rather than harboring the virus for years and spreading it, perhaps unknowingly, through sexual and needle contact. And the response, especially in the most advanced societies, of authorities to this knowledge will be dramatic. And so there is a reason the constant stream of new airborne viruses generated in Africa and Asia has not generated a new sort of Black Death, and is not likely to.


Anonymous Blue Cross of California said...

Great blog I hope we can work to build a better health care system. Health insurance is a major aspect to many.

4:04 AM  

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