As I was putting together a talk today about our microbial world, I just came across this interesting paper in the August issue of The Journal of Virology. A team of Korean scientists set up some traps to catch viruses and bacteria floating in the air. They set up their traps in Seoul, in an industrial complex in western Korea, and in a forest. Based on their collection, they came up with the following estimates... **In each cubic meter of air, there are between 1.6 million and 40 million viruses. **In each cubic meter of air, there are between 860,000 and 11 million bacteria. Given that we breathe roughly .01 cubic meters of air each minute, a simple calculation based on these results suggests we breathe in a few hundred thousand viruses every minute. Half of the viruses the scientists trapped didn't match any known virus species. But most belong to groups that infect plants or mammals. A note to hypochondriacs: holding your breath may keep viruses from coming into your body, but as a lifestyle choice, it has some drawbacks.