A 'Spider' being "The Web-walking part of a search engine that collects pages for indexing in the search engine's database. Also called a bot.":answers.com
I thought I'd better put that in, because when I first saw the title, I had visions of biologists, out in the wild, catching spiders to be tested for disease.
Now if you want to find out about disease outbreaks, you can just google them before the WHO Centres of disease control have any idea.
Maybe WHO should google not yahoo.

Great post, thanks for the infor.