According to Nathan Wolfe, a virus hunter interviewed last week in another TED Q&A, "We've created a perfect storm for viruses". An excerpt:
SARS, avian flu, swine flu ... what's going on here? Why are we suddenly seeing so many more outbreaks of viruses from animals?
Viruses have always passed from humans to animals. In fact, the vast majority of human diseases have animal origins. But the human population is different from what it once was. For most of our history, we lived in geographically disparate populations. So viruses could enter from animals into humans, spread locally and go extinct. But the human population has gone through a connectivity explosion. All humans on the planet are now connected to each other spatially and temporally in a way that's unprecedented in the history of vertebrate biology. Humans -- as well as our domestic animals and wild animals we trade -- move around the planet at biological warp speed. This provides new opportunities for viruses that would have gone extinct locally to have the population density fuel they need to establish themselves and spread globally.
We've created a "perfect storm" for viruses. And we'll continue to see -- as we have in the past few years -- a whole range of new animal diseases as outbreaks in human populations. But we have to stop being surprised by them. Right now, global public health is like cardiology in the '50s -- just waiting for the heart attack, without understanding why they occur or the many ways to monitor for them, detect them early and ultimately prevent them. Swine flu is not an anomaly. We know that swine flu -- like the vast majority of new outbreaks -- comes from animals. We should be monitoring those animals and the humans that come into contact with them, so we can catch these viruses early, before they infect major cities and spread throughout the world.
And here's Wolfe's TED talk: