Ignaz Philip Semmelweis (1818-1865) pioneered handwashing as a mechanism to help prevent the spread of septic infections in mothers following birth.  Though this was very effective, his contemporaries never accepted his ideas.

Joseph Lister (1827-1912) pioneered the use of antiseptic surgical techniques, utilizing phenol (carbolic acid) to disinfect surgical air, handwashing, and the draping of surgical wounds with boiled towels to discourage microbial infection.

Florence Nightingale (1820-1910) introduced antiseptic technique to nursing.  During the Crimean War (1854-1856) she developed standards of hygiene for military hospitals that would carry over to her school of nursing.

John Snow (1813-1858) was the father of the science of epidemiology, the study of the spread and prevention of infectious disease.  Through a careful mapping of East London during the cholera epidemic of 1854, he was able to trace the disease to a single well on Broad Street that had been contaminated by sewage.

Edward Jenner (1749-1843) pioneered the use of vaccination to control the spread of smallpox.  Jenner's work would influence many others, including Louis Pasteur, who developed vaccines against rabies and other infectious diseases.

Paul Ehrlich (1854-1915) pioneered the study of chemotherapy through his meticulous study of chemotheraputic agents against microbial infection.  Ehrlich was the first to discover the concept of "selective toxicity," meaning that a chemotheraputic agent could negatively affect a microbe while not causing damage to the host.  His work with arsenic derivatives in 1908 led to development of compound 415 which was effective against Trypanosoma and compound 606 (called Salvasin for "salvation from syphilis").  He hoped to find a "magic bullet" that would be effective against all forms of pathogens.