Final answer:
John Snow's contributions to epidemiology include investigating cholera outbreaks, mapping the distribution of cases, and supporting the germ theory of disease.
Step-by-step explanation:
John Snow, known as the father of epidemiology, made significant contributions to the field by investigating cholera outbreaks in 19th-century London. He was skeptical of the prevailing miasma theory and believed that cholera was spread through contaminated water. Snow collected data and mapped the distribution of cholera cases, demonstrating that all affected homes received their drinking water from a specific well that was contaminated with human feces. His work supported the germ theory of disease and led to the adoption of new public health measures.