On Apr. 10, 1972, the U.S., the Soviet Union and 70 other nations sign an agreement that restricted countries from developing, producing, stockpiling, or acquiring biological agents, weapons, and equipment outside of peaceful purposes. However, some signatory countries continued weapons development.

Advances in biotechnology have made it easier to develop dangerous viruses, bacteria, and toxins with fewer resources. This has increased concerns that individuals and groups could resort to bioterrorism to attack a population.