Have you ever wondered why milk is pasteurized? Pasteurization is a process that heats milk to a high temperature to kill harmful bacteria that can cause diseases. Thanks to pasteurization, we can enjoy milk without worrying about getting sick. But this was not always the case. In the early 20th century, many people suffered from a painful and debilitating disease called brucellosis, which they contracted from drinking raw milk. The person who discovered this link and fought for the safety of dairy products was Alice Evans, a pioneering microbiologist who faced ridicule and discrimination for her groundbreaking work.
Alice Evans was born in 1881 in rural Pennsylvania. She grew up on a farm and developed a love of nature and science. She attended Cornell University and earned a bachelor’s degree in agriculture in 1909. She then pursued a master’s degree in bacteriology at the University of Wisconsin, Madison, where she studied the bacteria that cause cheese to ripen. She chose not to pursue a Ph.D., but instead landed a job at the U.S. Department of Agriculture, working in the Bureau of Animal Industry’s Dairy Division.
It was there that Evans began studying what was to become her legacy-defining work on bacterial contamination of milk. She learned about two bacteria that were causing problems for humans and animals: Brucella abortus, which caused spontaneous abortions in cows, and Brucella melitensis, which caused undulant fever (also known as Malta fever) in humans. Undulant fever was a chronic disease that caused fever, muscle pain, fatigue, and depression. It was also known as “Mediterranean fever” because it was common among people who drank goat milk in that region.
Evans suspected that these bacteria were actually the same species and that humans could get sick from drinking cow milk contaminated with B. abortus. To test her hypothesis, she conducted experiments on pregnant lab animals and found that both strains caused abortions. She also tested the blood serum of the infected animals and found that they reacted similarly to antigens from both strains. These experiments provided strong evidence that B. abortus and B. melitensis were the same species and that they could cross the species barrier.
Evans published her results in 1918 and suggested that pasteurization of all milk could prevent the transmission of brucellosis to humans. However, her idea was met with skepticism and hostility from both the dairy industry and the scientific community. They argued that pasteurization was too expensive and unnecessary, and that brucellosis was not a serious threat to human health. They also dismissed Evans’s work because she was a woman and did not have a doctorate.
Evans faced many challenges and obstacles in her career as a woman scientist. She was paid less than her male colleagues, denied promotions and recognition, and excluded from professional societies and meetings. She also contracted brucellosis herself, which caused her chronic health problems for the rest of her life.
Despite these difficulties, Evans continued to work on brucellosis, helping to normalize the use of pasteurization and codifying safety procedures that have greatly reduced the disease’s impact. She also conducted important work classifying different strains of streptococcus before finally retiring in 1945.
Evans was a pioneer for women in microbiology and public health. She once said: “I had no idea I would ever be able to do anything worth while; I just wanted to do something useful.” She certainly achieved that goal, and more. Her work saved millions of lives by making milk safe to drink. She also paved the way for other women scientists to pursue their dreams and make their own contributions to science and society.