What's more, the AP has an article about a new strain of the HIV virus, possibly originating in Yaounde, Cameroon.
On top of that, there's daily news on the fatal A1H1 flu virus (a.k.a. swine flu) that I don't care to recount here.
Honestly, I don't think we have to fear a comet or asteroid impact or even global warming or nuclear warfare; I think the world (or humanity, at least) is going to succumb to bacteria and viruses.
(I honestly don't mean to sound pessimistic and apocalyptic. It's just food for thought.)