Only the recent viruses are suspected to be bio-weapon. Why do you inlcude things like Spanish flu, Lyme disease…
That’s not a logical argument at all. It’s very unlikely that nuclear catastrophes happen, but they do. A lot of thing “very unlikely” because “we take all the security steps” happen. It’s very unlikely to die from the lightning or to find a treasure, but it happen. But here, one little time is enough, one person is enough. Logically, your argument doesn’t mean it can happen, or it cannot happen: it means nothing.