How to prevent pandemics

It would be funny if it were not so serious. As migratory birds carry the avian influenza virus west across Europe, Britain is following in the footsteps of Russia, Ukraine, Romania and Turkey and asking hunters to shoot down as many incoming ducks and geese as possible. They have been issued with bird- flu testing kits to see if their victims are carrying the dreaded virus, but they really have little to worry about: all the cases of direct bird- to- human infection, now more than a 100 in total, have occurred on family farms in southeast Asia. The panic over bird flu is not wholly misplaced. If the H5N1 strain currently ravaging wild bird flocks learns to pass between humans while retaining even a tenth of its current lethality — the death- rate among people who catch it directly from birds has been as high as 50 per cent — the world would face an influenza pandemic as grave as the Spanish flu in 1918- 19 that killed between 50 million and 100 million people. Only in the past couple of decades has it been widely understood that almost all the quickkiller infectious diseases that have emerged to ravage human populations since the rise of civilization come from domestic animals. Human beings in the wild, like other predators that live in small, isolated groups of a few dozen individuals, would rarely have fallen victim to the killer viruses and bacteria whose natural habitat are animals that live in large herds. Even if such a disease did jump from some prey animal to the hunters who killed it, and even if it then adapted enough to infect the other members of the hunter- gatherer band, the new, humanform would usually die out when it had run through those few dozen people. Only when civilization brought people together in large groups, and those people began living in constant close contact with domesticated versions of herd- dwelling animals, did the killer diseases that often devastate those species begin to adapt permanently to humans. Over the past 3,000 to 4,000 years, this process has given us a range of highly infectious human diseases, including quite lethal ones like smallpox, cholera, typhoid, and the Black Plague. Influenza, which colonized civilized human beings via their flocks of domesticated birds, is usually a relatively mild member of this family of diseases. But the flu virus mutates with ease, and occasionally it assumes a highly lethal form. As our population has grown into the billions and the volume and speed of travel have soared, we have become more vulnerable to these “ emergent” diseases, but they are unlikely to emerge on a British or even a Russian farm.

Eighty years ago, the Spanish flu virus probably made its way from wild ducks into chickens and thence into human beings on a Kansas farm. But modern commercial farming does not involve people and their animals sharing the same living spaces. Moreover, if some disease does cross the species barrier anyway, its human victims are far more likely to get early treatment ( and, if necessary, quarantine). The places where the style of farming and the density of human and animal populations still favour the easy movement of diseases from animals into people are mostly in Asia, particularly in southeast Asia. That is where all the new flu viruses have emerged in the past half- century, where the SARS virus came from two years ago, and where other emergent diseases are most likely to appear. As a first step, it would make sense to create a network of trained observers who would report on any unusual disease patterns among the local farm families or their animals.

This is being done in Thailand, and much poorer Vietnam is making a start, but Indonesia has done little, the Chinese refuse to say what they are doing, and some of the smaller countries have done nothing.

In the longer run, farmers throughout the region must be encouraged to change their ways of raising poultry, pigs and other animals. The countryside wouldn’t be nearly so picturesque at the end of the process, but the world wouldn’t be facing so many new diseases, either. Gwynne Dyer is a Canadian journalist based in London whose articles are published in 45 countries.