The story of Mary Mallon, better known as Typhoid Mary, is often repeated and well-known by many a school child, so as to instill awareness about the possibility of asymptomatic carriers, disease transmission, and to promote better hygiene and hand-washing. I personally remember learning about her sometime between kindergarten and third grade.
Mallon was a cook who infected over 50 occupants of many households with typhoid between 1900-1915. At least three people she infected died, and it's assumed she likely infected more people than could be traced. The bacteria salmonella typhi causes typhoid fever, affecting the intestinal tract and the blood, with symptoms that include high fever, headaches, constipation, diarrhea, and fatigue, among others. You can definitely tell when someone is sick from typhoid, but Mallon never showed any signs of being infected at all.
She was confined to a hospital, but was eventually released on the condition that she no longer work as a cook. Unfortunately, she didn't have any other skills and she went back to work as a cook, and once she was again apprehended, she was forced to remain in quarantine for the rest of her life, adamantly refusing the notion that she was an asymptomatic carrier of typhoid. There were hundreds of other asymptomatic carriers of the disease that were found around the same time, but Mallon was the only one with such a sad fate.
The concept of an asymptomatic carrier was fairly new at the time and would only really have been known by a select few healthcare workers and scientists—not the general public, so it wasn't something Mallon could easily believe. One would think they could have allowed her to continue working as a cook, if they had imparted proper hygiene upon her...
Salmonella typhi's route of transmission is oral-fecal, and it's commonly acquired from contaminated water and food; other possible routes of transmission are from surfaces and flies. The bacteria can be found in both feces and urine, so, presumably, as a cook, Mallon failed to wash her hands after she used the bathroom on some—or all—occasions when she prepared meals for her clients; cooked meals are hot enough to kill the bacteria, but George Soper, the sanitation engineer who tracked her down, noted that on one particular day of the week, Mallon had prepared a cold dessert for her clients.
Hygiene—including hand-washing—became a more serious matter for surgeons when germ theory was developed in the mid-1800s, "and by the 1890s and into the early 1900s, handwashing moved from being something doctors did to something everybody had been told to do."
Of course, one shouldn't expect hand-washing was actually that regular or often for the average person. Though it's difficult to find information other than anecdotes from that time period, we can assume that more people wash their hands now. Clean (relatively speaking) water and soap are in most restrooms now and we're bombarded with advertising on the subject.
In a study of 404 bus and train commuters in the UK, 28% had fecal matter on their hands. Another study in northern England found that mothers washed their hands only 42% of the time after changing a dirty diaper; 1/5th of the subjects failed to wash their hands after using the toilet. A third study looked at 96 empirical studies and found a median compliance rate of only 40% for hand-washing (the authors add a caveat about the studies they looked at: "In general, the study methods were not very robust and often ill reported.").
In most cases, it's less crucial to wash the hands when feces isn't involved, but one study looks at No. 1 and 2 separately. "After urinating, 69% of women washed their hands, and only 43% of men," she says. "After defecation, 84% of women and 78% of men washed their hands. And before eating – a critical time to wash your hands – 10% of men and 7% of women washed their hands."
Even healthcare workers are often lax: "A study conducted in a teaching hospital at East Tennessee State University in 2007 found that staff handwashing between attending patients in all intensive care units (ICUs) had an overall compliance rate of just 54%. Staff in the paediatric ICU were much more conscientious, with 90% compliance, compared with just 35% in the adult ICU. After intervention and training, however, the compliance rate in the adult ICU was raised to 81%."
Mallon's story is illustrative of the possibility of asymptomatic transmission and the importance of hand washing and other forms of hygiene to reduce the spread of pathogens, but can it really tell us much about the current situation with Covid-19?
It's alleged that the theory of the "superspreader" originated with the story of Typhoid Mary, and this term has been increasingly used since at least the 1990s, rising in subsequent decades, and reaching a crescendo with Covid-19. So-called superspreaders can be symptomatic or asymptomatic, but asymptomatic and infectious could potentially yield the most effective rate of transmission, as no one will be aware they should keep their distance, and the carrier won't know to stay at home.
A quick search yields many results, such as "Opinion: Not planning to get vaccinated? Look up Typhoid Mary," "The Law and You: What does ‘Typhoid Mary’ have to do with COVID-19?," "What Typhoid Mary's Story Tells Us About COVID-19 Tensions," "'Silent spreaders' may be responsible for half of Covid-19 cases, study finds," and "To beat Covid-19, find today’s superspreading ‘Typhoid Marys’." All of the articles are about the dangers of asymptomatic spread, superspreaders ruining everything, and mulling over the detainment of those who don't want to wear masks or get vaccines.
Ultimately, the term superspreader tends to be used because it sounds scary, and what is considered a superspreader event is politically motivated—Trump supporters or anti-lockdown protesters gathering would be labeled a superspreader event by the media, whereas the BLM protests were praised as being important for social justice, and infectiousness suddenly didn't matter.
It became expedient to throw about the term superspreader to imply the unvaccinated or the unmasked were spreading their sick, when asymptomatic spread of Covid-19 appears non-existent. They've done the same to encourage vaccination by saying those who aren't vaccinated are superspreaders; of course, it's now widely admitted that the vaccines do not curb transmission rates, but instead reduce mild symptoms only... The main goal is to create paranoia and fear around a virus that is not anymore lethal than the flu.