>I doubt there could really come a bug that would actually wipe out a sizable portion of the humanity, simply because there are too many efficient and cost-effe

>I doubt there could really come a bug that would actually wipe out a sizable portion of the humanity, simply because there are too many efficient and cost-effective things we could do. Like institute effective quarantine measures, or basic hygiene, or vaccines. Maybe the rich, industrialized countries would be able to quarantine it quickly enough, but if it was released in, say, Africa, the governments there wouldn't be able to do much about it. Hygiene is helpful, but it only does so much against airborne pathogens, and even in hospitals where everyone is trained to wash their hands disease is spread all the time. As for vaccines, they take time to develop and deploy. Remember the H1N1 scare in 2009? That vaccine was in short supply at that time. Quantitatively, the only real data in this thread is that it's possible for a virus to kill ~80% of a population like myxamatosis (oops, it looks like I was wrong - it's more like 95%: http://books.google.com/books?id=wnlB7EMtqFYC&pg=PA427&dq=rabbit+myxomatosis+percent+of+the+population&hl=en&ei=6O3QTsOcEpLSiAK60bn-Cw&sa=X&oi=book_result&ct=result&resnum=7&ved=0CFUQ6AEwBg#v=onepage&q=rabbit%20myxomatosis%20percent%20of%20the%20population&f=false http://books.google.com/books?id=wnlB7EMtqFYC&pg=PA427&#... ) It's not obvious how much of a difference the factors you mention make. They could nip the virus in the bud so it only kills a handful of people, or they could make virtually no difference at all.