The Biological Weapons Convention (BWC) prohibits the production, use, development, stockpiling, or transfer of biological toxins or disease-causing organisms against humans, animals, or plants. More than 180 countries are party to the pact, which came into force in 1975 as the first multilateral treaty to ban an entire class of weapon. And in the years since, the taboo against state use of biological weapons has largely held. Yet a volatile geopolitical environment, combined with the rapid advance and increased access in the ability to edit and engineer pathogens, is straining and testing the nearly 50-year-old BWC as never before. From the BWC's beginnings, critics have said it lacked vital elements, like a verification mechanism to make sure everyone is following it. Global tensions, scientific advances, and the ever-expanding repertoire of what is possible with both biology and chemistry are making those flaws and cracks ever more visible. Some high-profile mishaps linked to the US chemical and biological weapons programs ... along with public anger over the use of herbicides like Agent Orange during the Vietnam War, prompted Congress to pressure the Nixon administration to review the biological and chemical weapons programs. Contagions are hard to control and contain, and the same pathogens that can infect your target can also sicken you and your population. This is also why they tend to be used as a stealth agent of war. "The holy grail that we've struggled with with the Biological Weapons Convention is how do you verify that the countries that have signed up to the treaty are not making biological weapons?" said Kenneth Ward, US special representative to the Biological Weapons Convention.