Salmonella is an important bacterial genus which causes one of the most common forms of food poisoning worldwide. Throughout history typhoid fever – caused by Salmonella enterica serovar Typhi – triggered many dire outbreaks, and people eventually recognized the link between this disease and contaminated food or beverages.
Karl Joseph Eberth, a doctor and student of Rudolf Virchow, discovered the bacillus in the abdominal lymph nodes and the spleen in 1879. After he had published his observations in 1880 and 1881, his discovery was subsequently confirmed by German and English bacteriologists, including Robert Koch.
The genus “Salmonella” was named after Daniel Elmer Salmon, a veterinary pathologist who ran a The United States Department of Agriculture (USDA) microorganism research program in the 1800s. Together with Theobald Smith, he found Salmonella in hogs that succumbed to the disease known as hog cholera.
The story of Mary Mallon
Mary Mallon was born in Ireland and immigrated to the United States in 1884. She is considered the first famous carrier of typhoid fever in the United States. Initially engaged in 1906 as a cook by Charles Henry Warren, a wealthy New York banker, she was subsequently hired as a cook at several private homes throughout the New York area.
Moving from household to household, Mary Mallon caused several typhoid outbreaks, always vanishing before an epidemic could be traced back to the particular household she was working in. Mary represents the first known case of a healthy carrier in the United States, and was proven responsible for the contamination of at least 122 people – including five dead.
In 1907 almost 3000 inhabitants of New York had been infected by Salmonella Typhi, with Mary probably being the main reason for the outbreak. Due to a lack of antibiotic treatment and no immunization option at the time, a dangerous source like Mary had to be restrained.
After police intervened and Salmonella had been found in Mary’s stool, she was transferred to North Brother Island to Riverside Hospital, where she was quarantined in a cottage. As she was the first known healthy carrier of typhoid fever in the United States, she did not understand how someone healthy could spread disease; hence she tried to fight back.
Although the New York Supreme Court dismissed her petition for release, the city’s new health commissioner Ernst J. Lederle took pity on Mallon and released her on the promise that she will never again work as a cook. Nevertheless, she was found to be working as a cook, which was again causing typhoid outbreaks. She was sent back to North Brother Island, where she lived until her death in 1938.
There is still much speculation regarding the treatment that Mary received at the hands of the New York’s Department of Health. Instead of working with her to make her realize she was a risk factor, the state quarantined her twice and turned her a laboratory pet. This case is often cited as an example of how the health care system provokes prejudiced social attitudes towards disease carriers.
Historians and scientists have studied outbreaks in the past and come to the conclusion that many of them may have been typhoid infections. Around the year 430 B.C. a plague thought to be an outbreak of typhoid fever killed one third of all the people in Athens, which at the time was one of the most powerful cities in ancient Greece.
Salmonella infections have been present in America since at least the early 1600s. Scholars studying the history of Jamestown in Virginia believe that a typhoid fever was responsible for deaths of over 6000 settlers between 1607 and 1624. Typhoid fever was the major killer in the Spanish-American war of 1898 as well.
Due to vaccinations and advances in public sanitation, the incidence of typhoid fever in developed countries plummeted to approximately 5 cases per one million people per year. Nevertheless, outbreaks caused by other Salmonella serovars are commonly observed.
One of the deadliest Salmonella outbreaks occurred in 1985, when approximately 6149 cases of Salmonella Typhimurium were reported among people who had consumed 2% pasteurized milk sold in the northern Illinois (of which 5770 were laboratory-confirmed).