Rhazes, the chief physician of a Baghdad hospital, gives the first scientific description of smallpox and establishes criteria for diagnosing the disease. By 1350, it will have killed about half of Europe's population. The vaccine works, but Jenner is vilified. Louis Pasteur demonstrates that infectious diseases could be prevented by injected attenuated microbes, using this vaccination treatment successfully on young Joseph Meister, a victim of rabies.
Tuberculosis is the second leading disease killer.
The fist Nobel Prize in medicine goes to Emil von Behring for his diphtheria antitoxin. Typhoid fever breaks out in New York City, and the epidemic is traced to one Mary Mallon, a carrier of the disease who does not get it but spreads it by taking a variety of food-handling jobs, using assumed names. German bacteriologist Paul Ehrlich formulates an arsenic compound to fight syphilis. The medicine will reduce the incidence of syphilis in England and France by 50 percent over the next five years. A U.S. company produces equine-based tetanus and diphtheria serums that are used to inoculate Canadian soldiers leaving for the war in Europe.