Here’s an interesting thought: if someone patented (or copyrighted, or what have you) the cold virus, could they sue people for propagating their intellectual property without permission? Or could the hapless victims sue them for not keeping a dangerous virus under proper control? Of course, the very idea is ludicrous, but so are a lot of things about intellectual property law.
Old-Fashioned Fruitcake
I believe there are laws (not sure how widespread) to the effect that anything created by nature cannot be patented. Were this not the case, I’m not sure if people would want to copyright/patent an infectious disease, for precisely the reason you gave: anyone could hold them accountable for not properly controlling their property.
And yet, there are “almost 11,000 patents involving HeLa cells” according to Wikipedia. Of course, that means they’re not purely as nature produced, but it’s still weird and kind of squicky.