Transcript:

Viruses: A Sense of ScaleMcDonald: One of the reasons for the our lack of our knowledge about viruses is really based on how tiny they are. This week we've been taking a close look at viruses, something that historically has not been so easy to do because they're so small. I'm Jim Metzner and this is the Pulse of the PlanetMcDonald: They're 100 to 1,000-fold times smaller than a bacterium. Sarah McDonald is an assistant professor at the Virginia-Maryland College of Veterinary Medicine and the Virginia Tech Carilion Research Institute. McDonald: Some of the earliest historical identifications of viruses as entities that cause disease - and their being different than other germs like bacteria and other types of parasites, was based on the advent of pasteurization. Pasteurization is a process in which you can filter fluids or water, and the size of the filter was able to trap bacteria and other bigger germs. But what happened is that the viruses - and at this time, we didn't even really know what they were - would actually pass through the filter.And it wasn't actually until I would say around 1950 that we actually were able to visualize viruses for the first time. Because of their small size, we need very powerful microscopes called electron microscopes to see them. We cannot see them with a visible light microscope. And so, it's really only very, very recently that we've been able to actually see what these germs look like.If we think of the virus sitting on the surface of a soccer ball, and then we imagine the soccer ball is now the size of the planet earth, the analogous size of what a virus would be is essentially a car. If you imagine a car sitting on the planet earth, that would be the same size dimensions relative to a virus sitting on the surface of a soccer ball. They're super tiny.We'll hear more on viruses in future programs. I'm Jim Metzner and this is the Pulse of the Planet