When hantaviruses hit the headlines with the advent in May 1993 of a new disease in the USA, and later in the New World from Canada to south Argentina, called "hantavirus pulmonary syndrome" (HPS), speculations in the lay press rose from the very beginning around the possibilities of a biological warfare (BW) weapon. Indeed, the responsible agent of HPS, hantavirus, was almost unknown at that moment in the New World, was airborne, seemed to target preferentially young adults, and induced a devastating cardio-pulmonary collapse with a high case-fatality rate (50%), often within hours. It quickly became clear, however, that the same scourge had been known for many years in the Old World under different and mostly milder presentations. With the rapidly increasing knowledge about hantaviruses, it also became clear that they lack many of the potentials of an "ideal" BW weapon, as will be explained in this paper.