Click Here for last week’s article: Part Two ‘Whatever Happened to the Bubonic Plague and what has Chickenpox got to do with it?

Part Three of Weekly Series:

The Many ‘Typhoid Marys’

Typhoid fever facts, information, pictures | articles about typhoid fever

Typhoid fever is passed from person to person through poor hygiene, such as incomplete or no hand washing after using the toilet. Persons who are carriers of the disease and who handle food can be the source of epidemic spread of typhoid. One such individual gave her name to the expression “Typhoid Mary,” a name given to someone whom others avoid.
 Gale, T. (2006)
Typhoid Fever, Gale Encyclopedia of Medicine, 3rd ed.

But, as it turns out, Mary Mallon, the silent carrier of Typhoid Fever, was not actually as deadly as her infamy would lead us to believe. It is simply that her case was the most publicised at the time.


“Mary Mallon was born in 1869 in Cookstown, Co Tyrone. She emigrated from Ireland to the United States in 1884.

Mallon became the focus of one of the best-known episodes in the history of communicable disease when U.S. health officials identified her as a healthy carrier of the organism causing typhoid fever. Mallon, who refused to acknowledge her role in spreading the disease as a cook, is known to have infected at least 53 people, resulting in three deaths. Unable to stop her from cooking for others, New York City authorities confined her for 26 years…”
Stair na hÉireann/History of Ireland (2014)

I am sure if we could explain to Mary back then (but no one knew at that time), that she simply could not feed anyone uncooked food – no matter how delicious her recipe for frozen peaches was, and still would have been able to maintain herself through work and not spend more than a quarter of her life in captivity with threats of removing her gallbladder.

Mary mostly cooked for wealthy families, some of which she inadvertently infected, and as you will see below, she also infected other well-scrubbed and well-fed individuals such as, doctors, nurses and medical staff at a maternity hospital. Essentially, people who would have had the least exposure from their environment of such a pathogen.

Refusing Quarantine: Why Typhoid Mary Did It

Health officials lost track of her for a few years, but found her again in the midst of another typhoid outbreak, this time at a Manhattan maternity hospital where 25 people, mostly doctors and nurses, were infected. Mary had been cooking there under a fake name, but fled before health officials could catch her. They traced her to a house in Queens, where they had to sneak in through a second-story window, using a ladder, to apprehend her, according to the Times report on the event.
Latson, J (2014) , Time Magazine (Nov., 11th 2014)

In some ways, as tragic as the few deaths were that Mary inadvertently caused, look how many people she infected (particularly the most hygienic health professionals as they probably had managed to avoid such an unhygienic infection up to this point in their lives), and did survive to tell the tale, thus leaving them with immunity from the disease for life. Moreover, her spate of silently spreading the disease to previously unexposed individuals should be viewed in the context of the bigger picture of the devastation the disease itself had caused amongst populations both within Ireland, her homeland, and across the Atlantic.

Typhoid Fever Mortality Ireland

Fig. 1: Chart of the annual number of deaths in Ireland from Typhoid Fever since records for this disease began. Note the dramatic decline throughout the late 19th Century through to the mid 20th Century. Source: Chart generated using annual statistics reports since records began – “Annual Reports on Marriages, Births and Deaths in Ireland, from 1864 to 2000” courtesy of An Phríomh-Oifig Staidrimh, Central Statics Office CSO, link. © Copyright

When the rate of annual deaths from Typhoid Fever are compared between the U.S. and Ireland we find a near identical decline for a similar timeframe where the main difference is simply a matter of scale. I.e., the U.S. population being much greater than that of a tiny country like Ireland, the proportions of deaths per population from Typhoid would have been similar, but of course the  actual total numbers of deaths per year in the U.S would have been in the tens of thousands.

For instance, a graph [4], Figure 16, p. 82, Vital Statistics Rates, Death rates for Typhoid Fever: Death –registration States, 1900-32, and United States, 1933-60, based upon rates per 100,000 population show that at its height,  there were 32 deaths per 100,000 per year starting at 1900 (in a population of a couple of hundred million, that’s a lot of deaths) and declining to less than 20 deaths per 100,000 dramatically dropping from 1910 onwards and from the 1920s, this downward trend continues until deaths from Typhoid Fever becomes very rare by the 1960s.

In Ireland, (See Fig. 1), the deaths per year from Typhoid Fever had become almost a rarity by the 1920s and 30s, with a slight peak in the 1940s and then practically unheard of after this period. The Irish had seemingly won their battle against the disease, as did Americans. In other words, in the scheme of things, Typhoid Mary was a drop in the Atlantic Ocean when it comes to being responsible for the spread of Typhoid Fever in the States.

By the time Mary Mallon had landed as an Irish immigrant on the U.S. shores, deaths from Typhoid Fever were already on the brink of free-fall, suggesting that the vast majority of people were well on their way to becoming immune to the disease already. Almost everyone had most likely already been exposed to the Typhoid, whether they knew it or not, and had become immune for life. This is reflected in the statistical data, indicating that generations had already become resilient and hardened to the disease, making it increasingly more difficult for the pathogen to gain a foothold in these populations as a whole. Was Mary alone in not remembering that she had the disease, or perhaps she was correct when she said she never had any symptoms at all.

As it turns out, she was not the only ‘Typhoid Mary’ type – apparently there were many others just like her, but of course, they weren’t all called Mary. Although her case is certainly the most famous, being a silent, or latent carrier of Typhoid was not actually that uncommon.

Typhoid and Paratyphoid Fever

About 1 in 300 people infected with typhoid fever may have a low-grade infection.
They may not develop any significant symptoms, and then become carriers of the disease’.
Tidy, C. (2018)

That’s not taking into account the ones that were infected but didn’t know it for some time after as symptoms develop late in this disease as also indicated in the rest of the article excerpted above. So you can perhaps begin to imagine how much of the population in both Ireland and the United States had already had exposure to the disease and built up community immunity from having survived it.

This begins to make sense of the steep decline in deaths in both nations over a similar course of time, and how the pathogen was dramatically losing its grip on the population as a whole – it was running out of options to colonise new hosts – fresh victims now only remained in small pockets of previously unexposed individuals. But what if we imaged for a moment that Mary was put on a boat and set out to sea, maybe to keep her company they gathered up all the known silent carriers. ‘Typhoid Mary’ and her merry band of exiles, although, not as lethally infectious in the scheme of things back home, due to so many having already built up resistance, if they happened upon a previously naive native population who had absolutely no immune resistance or experience to these foreign pathogens, their arrival would be devastating, at least initially.

The vessel carrying the bunch of ‘Typhoid Mary’ types, would not be that different from what has been all too commonly documented historically, particularly when explorers and colonisers of the so-called New Worlds of the Americas and Southern Latitudes arrived as silent carriers showing no signs of diseases or particular ill-health themselves, yet little did anyone know until the previously uninfected Indigenous Peoples begin dying in great numbers that what had happened began to sink in – old pathogens within previously exposed and now resilient populations had found new virgin territory to colonise.

Charles Darwin – the great evolutionist, directly quotes and comments on such incidences in relation to his own experience whilst on his adventures to the South seas in the Beagle.

CHAPTER XIX Australia in 1836:

The Rev. J. Williams, in his interesting work, … says, that the first intercourse between natives and Europeans, “is invariably attended with the introduction of fever, dysentery, or some other disease, which carries off numbers of the people.” Again he affirms, “It is certainly a fact, which cannot be controverted, that most of the diseases which have raged in the islands during my residence there, have been introduced by ships; … and what renders this fact remarkable is, that there might be no appearance of disease among the crew of the ship which conveyed this destructive importation.”
This statement is not quite so extraordinary as it at first appears; for several cases are on record of the most malignant fevers having broken out, although the parties themselves, who were the cause, were not affected.
Darwin, C (1839)
In :Alice Bergfeld – Rolf Bergmann – Peter v. Sengbusch BOTANY Online – The Internet Hypertextbook 2004.

Historically, this was an all too common phenomenon, but thankfully, it would seem that most of the world has had experience with many of these much deadlier infectious contagions and they are now incredibly rare, at least in our more developed nations. Interestingly, there is an indication from the literature in general that these same diseases are becoming rarer in less developed nations too. It looks like Nature is on the case and as you will see below, there is strong evidence to suggest they too will soon be looking back at their mortality statistics and seeing a similar pattern of plummeting deaths as we have thankfully experienced now in the developed world.

For example, the article excerpt below describes the historical devastation from Europeans – who were like Typhoid Mary and her band of silent carriers of plague-like proportions as given in accounts from when these new settlers and adventures began to colonise the Americas from the 16th Century onwards. However, it also offers hope, as it describes the natural resilience that can come about from having exposure to such pathogens circulating in general.

Rationalizing epidemics: meanings and uses of American Indian mortality since 1600

Europeans encountered new populations, in Hispaniola and Mexico in the 1500s, in New England and Quebec in the 1600s, and even in Alaska and the Amazon in the 1900s, they witnessed terrible mortality. Epidemics of smallpox, measles, and influenza took the highest toll. These diseases, endemic in Europe, had not been present in the Americas before European arrival. Europeans, exposed as children, developed immunity that protected them as adults. American Indians, without this immunity from prior exposure, and stressed by the chaos of European colonization, were dangerously vulnerable. They died in great numbers…
 Jones, D.S. (2004)
Rationalizing Epidemics: Meanings and Uses of American Indian Mortality since 1600. Cambridge: Harvard University Press, p. 26

The above excerpt reveals that seemingly, the Europeans themselves, due to exposure as children had become rather resilient to such previously devastating plagues, to the point where they all became ‘Typhoid Mary’ types, and although it was initially devastating to the previously unexposed natives, there is actually a possitive side to this story as that surely, if the Eurpeans had become immune generations before, then so could the natives themselves. The Europeans would have once been in the same boat generations before. The article excerpt below lends some support to this idea:

Immune Aspects of First Contact Epidemics

Isolated island populations were clearly subject to disastrous outcomes when new infectious diseases were first introduced, but this often did not extend to subsequent epidemics by the same pathogen…
Mathematic models make it clear that whatever the reason the extreme mortality rapidly decreased after the first-contact epidemics on Pacific islands, it was not due to Darwinian selection of disease-resistance genes. The time interval of only 2–3 generations is simply too short to involve such putative disease-resistance genes.
Shanks, G.D. (2016)
Am J Trop Med Hyg. 2016 Aug 3; 95(2): 273–277. doi: 10.4269/ajtmh.16-0169
Lethality of First Contact Dysentery Epidemics on Pacific Islands

We have only in more recent times began to gain more insight into just how adaptable and responsive the immune system actually is. Seemingly, just about every living thing can rapidly respond and defend itself from danger and threats, particularly disease, without having to wait around for millions of years in hope that we might end up with the lucky genes that will save us in the end. In other words, as indicated in the excerpt above, adaptation and resistance to disease can be handed down through generations and goes directly againt our current dogma of genetically-driven adaptation as the following excerpt title highlights:

Your Immune System Is Made, Not Born

New research dispels the belief that the strength of the body’s defense system is genetically programmed
…genes themselves need instructions for what to do … Those instructions are found not in the letters of the DNA itself but on it, in an array of chemical markers and switches, known collectively as the epigenome, that lie along the length of the double helix. These epigenetic switches and markers in turn help switch on or off the expression of particular genes. Think of the epigenome as a complex software code, capable of inducing the DNA hardware to manufacture an impressive variety of proteins, cell types, and individuals.
Landhuis, E. (2015)

You see, Nature may not be in the business of only allowing the fittest to survive, but ensuring that we all survive via a very different flexible non-genetic epi-genetic code  and one of the ways this is done in via our mothers.

Immune Priming: Mothering Males Modulate Immunity

Non-genetic transfer of immunity from mother to offspring is a well-recognized phenomenon known as transgenerational immune priming. Mammals, for instance, exchange immunological information on abundance and composition of pathogens to offspring via the placenta and antibody-rich mother’s milk…
The paradigm is that offspring who are destined to be raised in a similar disease environment to their mothers will benefit from a maternal enhancement of offspring immunity that reflects the current environmental challenges.
Keightley M.C., Wong B.B.M, and G J. Lieschke (2013)

It also now looks like we can inherit this hard-fought-for immunity, not just from our mother’s directly, but from their mother’s and perhaps generations of mothers before them as suggested by the following study – at least in pigeons.

Grandmothers can pass immunity to their grandchildren, at least in pigeons

At the moment of birth, a newborn leaves behind its safe protective environment and enters a world teeming with bacteria, parasites, viruses, and infectious agents of all sorts. However, the babies do have one trump card: antibodies and immune compounds passed across the placenta from their mothers. These short-lived molecules can dip into mom’s immunological experience to protect the newborn until the immune system gets up to speed. Now, a new study in pigeons suggests that some baby birds owe their early immunity not just their mothers, but to their grandmothers as well.
…previous research has suggested that these early maternal immune compounds may have “educational effects” on the newborn’s developing immune profile—that they may somehow be priming the system to be on the lookout for common local diseases or parasites…
Shultz. D (2015)

In other words, it is now looking quite likely that our immune systems can memorise past battles with pathogens – epigenetic imprinting which is generational – i.e. these adaptations can be inherited along with your genes and we can pass those experiences and expertise gleaned from the battles to our offspring.

You see, your immune system, as we are coming to appreciate in more recent times, as we gain more insights into tiny biochemical and molecular world beyond the relatively fixed and unchanging genes, is just as clever and flexible as the pathogens themselves.  Most of us have heard of antibiotic resistant strains of bacteria and how bugs can become superbugs due to their rapid adapation to our efforts to eradicate them? Well, our immune systems also adapt rapidly to pathogens, it is just that we are more complex and bigger than bacteria, so it might take us a few generations for the whole community to become robustly immune as suggested by the mathematically model study highlighted earlier.

Unfortunately, there are casualties, particularly when a pathogen that our immune systems are not familiar with gains a foothold, as illustrated by the large number of deaths from Typhoid Fever in the earlier days since records began as seen in the Irish chart and discussed for the U.S. Our immune systems are built to adapt to and withstand all sorts of pathogens as illustrated so clearly, not just in the mortality charts for Typhoid, but for all the other highly infectious disease that were once significantly more deadly as the record clearly shows.

Therefore, it seems that the more the immune system is exposed to the pathogen, directly, or indirecly as it silently circulates in the natural background (bear in mind that the Typhoid causing pathogen never went extinct, it is still with us today), the more adept our immune system becomes at defending us. In effect, each exposure – even if we are not sometimes aware of the pathogen circulating, trains and educates our immune systems to deal with just about everything in the end.  And now, it looks like this immunity is not just for life if you survive the ordeal, or even have to experience the disease  directly to gain general resistance,  but that immunity may be inherited as well.

And just one more point on this long-term, non-genetic generational immunity. This means that there is hope for us even today, if for some reason one of these much deadlier contagions did erupt out into our modern-day world (perhaps via an intentional bioweapon), we may not have to fall about dying to build up community immunity all over again. This is supported in the following excerpt, which suggests that the disease doesn’t even need to be circulating in an obvious way for us to still build up and retain resistance to it. In other words, we may have now forgotten those diseases, but our immune systems have not.

Rethinking the Origin of Chronic Diseases

Some modern-day diseases reflect the capacity of organisms to “memorize” responses to external signals and transmit them across generations; …
 the original causative agent may not be extant today, but “memory” of the infection has persisted.
Shoja, M.M  et al, (2012)
BioScience, Volume 62, Issue 5, 1st May 2012,

So perhaps now you might see Mary Mallon’s story with a slightly different lens when we realise that being exposed to pathogens, in the broader scheme of things, although tragic for the few that lost their lives, there is actually a positive aspect underlying this means of infection via a healthy silent carrier of the disease.

It seems that we have our ancestors to thank for taking the greatest hit for us. Recall that each person who Mary infected (remember most survived), not only gained life-long immunity, but they gained something of even greater value – generationally immunity that they could then pass on to their own offspring for the future. We are that future.

Next week: Part Four: From Typhus to Typhoid.

Fill in the contact form below for updates on the Ten Part weekly series: Don’t Count your Children Before they’ve had the Pox.

References to Part Three

[1]  Gale, T. (2006) Typhoid fever facts, information, pictures, Gale Encyclopedia of Medicine, 3rd ed. [Available online]
[2]  Stair na hÉireann/History of Ireland (2014)  1938 – Death of Mary Mallon (Born in Cookstown, County Tyrone), Also known as Typhoid Mary [Available online]
[3Latson, J (2014) Refusing Quarantine: Why Typhoid Mary Did It, Time Magazine (Nov., 11th 2014) [Available online]
[4], Grove, R.D. and Hetzel, A.M.  (1968) Vital Statistic Rates in the United States, 1940-1960, U.S. Department of Health Education, and Welfare Public Health Service, Washington D.C. National Centre for Health Statistics (Figure 16, p. 82 Vital Statistics Rates, Death rates for Typhoid Fever: Death –registration States, 1900-32, and United States, 1933-60), [Available Online].
[5] Tidy, C. (2018), Typhoid and Paratyphoid Fever [Available online]
[6] Bergfeld, A, Bergmann R. and Sengbusch, P.V. (2004), Charles Darwin (1839), CHAPTER XIX :Australia in 1836,  BOTANY Online – The Internet Hypertextbook 2004.[Available online]
[7] Jones, D.S. (2004)  Rationalizing Epidemics: Meanings and Uses of American Indian Mortality since 1600. Cambridge: Harvard University Press, p. 26
[8] Shanks, G.D. (2016) Immune Aspects of First Contact Epidemics, Lethality of First Contact Dysentery Epidemics on Pacific Islands, Am J Trop Med Hyg. Vol. 95 [2], pp. 273–277. doi: 10.4269/ajtmh.16-0169 [Available Online]
[9] Landhuis, E. (2015), Your Immune System Is Made, Not Born, Discovery Magazine (Jan., 29th 2015)  [Available online]
[10] Keightley M.C., Wong B.B.M, and G J. Lieschke (2013) Immune Priming: Mothering Males Modulate Immunity, Current Biology, Vol. 23, [2] pp. 76-78 [Available online] doi:org/10.1016/j.cub.2012.11.050
[11Shultz. D (2015) Grandmothers can pass immunity to their grandchildren, at least in pigeons, (Nov. 10th 2015), [Available Online]
[12]Shoja, M.M  et al, (2012), Rethinking the Origin of Chronic Diseases, BioScience, Vol, 62, [5], [Available online]

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