Among diseases of man and beast, anthrax stands as one of the oldest known and certainly one of the most storied. (It is thought to be what Homer meant by the “burning plague” in the Iliad.) Once a common killer of grazing animals, it was also a lethal occupational hazard for humans who worked with infected hides and livestock. Yet the cause of anthrax remained a menacing enigma until well into the 19th century, when an unassuming German country doctor entered the picture to help name it and tame it.

In the 1870s Robert Koch set out to confirm that firecracker-shaped bacterial cells in the syrupy blood of anthrax-felled livestock (first isolated by French scientists a decade earlier) were what was killing the herds and flocks. Despite a lack of scientific equipment, Koch ran painstaking trials out of his home on possible routes of transmission. In 1876 he packed up his slides and took the train to Breslau (then in Germany) to present convincing evidence to a packed room of skeptical experts that spores shed by the bacterial rods (now known as Bacillus anthracis) could survive in dirt and launch infections in new hosts. Proceeding from that knowledge, Louis Pasteur in France, on whose work Koch had built, created an anthrax vaccine within four years.

In a historical moment, medical science changed. Bolstered by similar successes against tuberculosis and cholera, the new model replaced the prevailing view that diseases were spontaneously generated (by forces unknown—vengeful gods, perhaps). Diseases were finally better thought of as the signature of contaminants and pathogenic interlopers.

Unfortunately, starting in the 1930s, various nations experimental adaptation of anthrax spores as weapons renewed the dread over the ancient scourge. An international treaty banned all bioweapons development in 1972, but the Soviet Union at least seems to have continued to work on anthrax weaponization for some years. Then came the unsolved mail-based post-9/11 anthrax attacks of 2001. They sent vaccine labs in the U.S. into heavy production mode, and researchers burned through some five billion R&D dollars trying to get ahead of what the Centers for Disease Control and Prevention call a “class A” agent—the bioterror category deemed the highest threat to public health. Scientific knowledge can thus take life or give it, depending on whether it is in the hands of a brilliant loner with grace or a brilliant loner with grievances.