Click Here for last week’s article: Part One & Intro

Part Two of Weekly Series:

Whatever happened the Bubonic Plague and what has Chickenpox got to do with it?

BBC History

‘there were hardly enough living to care for the sick and bury the dead’
…scarcely a tenth of mankind was left alive.
James, 2011, ‘Black Death: The lasting impact’  

A plague tsunami swept across Europe in the year 1348 wiping out more than a third of its population. By the late summer, the Black Death descended upon Irish shores with a particularly harsh impact in the urban centres which took its greatest toll in the dead of winter. Spreading out in a second wave reaching its tentacles beyond to the most desolate hills in search of fresh victims, this plague knew no social boundaries as Nobles, Clergy, Merchants and Peasants either survived the disease – gaining immunity, or succumbed and died.

‘1348: A Medieval Apocalypse – The Black Death in Ireland’

1348 was one of the darkest years in European history. The most deadly of all diseases – the Black Death – swept across the continent reaching Ireland in the late summer. Within twelve months over one-third of the population had died. Towns and villages were abandoned.
Dwyer, 2016. Book Synopsis 

…But, Rats and their fleas may not be guilty after all…

rat heap

Fig. 1: The Grime Reaper Rat on a pile of rat corpses. Illustration of what archaeologists should have found, but didn’t – thus indicating that rats and their fleas may be innocent in being the true cause of the rapid and widespread devastation of the Plague during the middle ages.

Now looking at the archaeological evidence, as it turns out, there is a serious lack of evidence for great heaps of dead black rats.

‘Black Death? Rats and fleas finally in the clear’

…Archaeologists and forensic scientists … have examined 25 skeletons … Analysis of the bodies and of wills registered in London at the time has cast serious doubt on “facts” that every school child has learned for decades: that the epidemic was caused by a highly contagious strain spread by the fleas on rats…
Mortality continued to rise throughout the bitterly cold winter, when fleas could not have survived, and there is no evidence of enough rats… In sites beside the Thames, where most of the city’s rubbish was dumped and rats should have swarmed, and where the sodden ground preserves organic remains excellently, few black rats have been found.
Thorpe, 2014, 

As noted above, we also know that the plague was spectacularly lethal during the winter months and the fleas that are supposed to be the culprits in spreading it via black rats, would not have been able to survive in this late season. Similarly, this was also the case in Ireland judging by the historical records.

‘Unheard of mortality’ The Black Death in Ireland

The plague raged in Dublin between August and December, setting a pattern for the terror it would spread through other parts of the country…
Thorpe 2014, ‘Black Death? Rats and fleas finally in the clear’

So if no amount of cleaning up rat infestations could have curtailed the spread – as the rats and their fleas now appear to be off the hook, what caused such a devastatingly rapid and severe spread of this great pestilence?

A clue might lie in the following. If anyone is old enough to remember actually singing this little rhyme below, having no idea whatsoever what we were singing about, then you might be interested to know what it was all about.

Ring a’ ring a rosies,

A pocket full of posies,

A Tishoo,a tishoo,

We all fall down.

Bugl, 2008, 8, ‘History of Epidemics and Plagues’ 

Apparently, according to Bugl in the History of Epidemics and Plagues’, the common interpretation of the Rosies refers to rosary beads (the religious item used for prayer – presumably in the hope that this would provide protection from the plague and imminent death) and the part of the rhyme when the children hold hands, forming a circle, presumably indicates the ring.

It seems that the pocket full of posies suggests wildflowers to mask the odour of plague victims. However, further research on the medical interventions of the era would indicate that flowers and herbs (posies) may have been used as protection as well. But, perhaps the most interesting part of the rhyme which gives us the big clue, is that last line (the fun part for children if you didn’t know any better, as they all collapse unto the ground in a giggle at the end), relates to a mock sneezing “A Tishoo, A Tishoo,” – which strongly points to the pneumonic (lung) form of transmitting the plague rather than the bubonic means of transmission, as they all fall down after being sneezed on.

As the article excerpt below indicates, the pneumonic and bubonic plague are essentially the same disease; and are simply manifested in different ways within the body.

Risk of Person-to-Person Transmission of Pneumonic Plague

Bubonic plague never spreads directly from one person to another. The bacteria may reach the lungs of people through hematogenous spread… Pneumonic plague is the only form of plague that can be transmitted from human to human.
Kool and Weinstein, 2005

Therefore, the sneezing form (pneumonic) can originate from the bubonic plague by making its way into the lungs via the bloodstream (hematogenous – meaning to spread by the blood) (see below),, as suggested above. This lends greater support to the means by which the Plague could have spread with such initial devastation – now having a way to directly pass from person-to-person. In other words, we do not necessarily require rats and their fleas to explain the wildfire type spread of this disease, at least during the Middle Ages.



1. Producing blood.

2. Originating in or spread by the blood.

Stedman’s Medical Dictionary (2002)

We can now begin to imagine how the Plague could have possibly arisen  and gotten a foothold – at least initially via infected rats in its bubonic form (hence the term Black Death in some cases), and if it had found a way of entering the bloodstream which, we now know is medically possible and common enough judging by modern studies, we can see just how more easily spreadable the pneumonic form (via sneezing etc) would be compared to the rat/flea-borne bubonic plague form – which would have been more easily spotted than the sneezing form.

We could, therefore, suggest that the flea-infested rats may have been the spark, but the uninitiated population (new virgin hosts for the pathogen) provided the kindling and it all went up like a tinderbox as the growing European shipping commerce fanned the flames of the burgeoning metropolitan centres during the Middle Ages.

However, the good news is that, just as rapidly as this devastation spread, it also appears to have burnt itself out almost as swiftly. Seemingly, it had consumed just about all that it could find in its path and those that remained standing would have become immune because of it.

The Black Death in Ireland


Today we have the benefit of hindsight. We know, as fourteenth-century people suspected, that the mortality caused by the bubonic plague of the Black Death was the worst demographic disaster in the history of the world. We also know that the mortality came to an end in the first outbreak soon after 1350; contemporaries could not have known this would happen – so far as they were concerned everyone might well die…
Kelly, 2001, ‘Unheard-of Mortality’ 

As the plague was virtually unheard of after the 1350s in Ireland and most other parts of Europe, one might wonder where it went and would we survive the Plague if it rekindled itself? As it turns out, it did come back within historical living memory as documented for Ireland as we prepared for its reemergence as described below:

1900: Ireland’s last bubonic plague scare

While bubonic plague evokes images of the Middle Ages, Ireland has had more than one brush with the dreaded disease. As recently as the year 1900, ports across Ireland prepared for an imminent outbreak of the Black Death…
…The last great plague scare in Ireland began after the illness broke out in Glasgow in August 1900. Ireland with its constant and frequent traffic with the Scottish port was immediately at risk of infection… As the death toll in Glasgow reached 13 by September 8th 1900, petty politics in Ireland hamstrung preparations to prevent an outbreak… Nevertheless in spite of such attitudes all vessels arriving in Ireland from Glasgow continued to be subjected to rigorous checks. Meanwhile the Glaswegian authorities, not only isolated those who contracted the disease but also those who lived in close proximity to them. This drastically reduced contagion and by the end of September there was a dwindling number of new cases.
Dwyer  2016, ‘1900: Ireland’s last bubonic plague scare’

Fortunately, the new cases began to quickly fade as indicated above, and perhaps it was to do with the containment measures, but more recent outbreaks would suggest otherwise. For instance, modern-day incidences and more recent historical experiences with outbreaks are rather puzzling as the Plague itself, even in its pneumonic form doesn’t appear to have the great impact that it once had. I.e., even if it does escape out into the unsuspecting public, which it has done on a number of occasions in more recent times, it has thankfully turned out to be surprisingly tame.

Plague has received much attention because it may be used as a weapon by terrorists. Intentionally released aerosols of Yersinia pestis would cause pneumonic plague. In order to prepare for such an event, it is important, particularly for medical personnel and first responders, to form a realistic idea of the risk of person-to-person spread of infection…
The disease resulting from direct infection of the airways is usually called primary pneumonic plague. This form would also occur after an intentional release of aerosolized Yersinia pestis…
Since 1925, person-to-person transmission of pneumonic plague has not been documented in the United States. From 1925 to 2003, there were 447 cases of plague reported to the CDC, and 48 developed into secondary pneumonic plague. Thirteen cases of primary pneumonic plague were reported in the same period; 5 of these were caused by cats with plague pneumonia, 1 was associated with caring for a sick dog, and 3 cases were laboratory-acquired.
In 4 cases, the origin of the infection remained unknown (CDC; unpublished data) … None of the contacts of these 61 patients with pneumonic plague seem to have developed the disease.
Kool and Weinstein,  2005  

One of these cases is worth reviewing in order to demonstrate just how tame the plague appears to have become compared to when it was circulating in the Middle Ages. For instance, although its only victim did unfortunately die, it was discovered after the fact that she had the real pneumonic Plague form – (they thought she had actual pneumonia at first as Plague is so rare these days) and it was sometime later when she had already exposed quite a number of people, including small infants in the day-care centre where she worked, that the penny finally dropped when the medical people realised what had just happened. This is described in the excerpted article below:

Discover Magazine

‘Will the Black Death Return?’

On October 2, 1980, a 47-year-old woman from south lake Tahoe, California, lost her 9-month-old pet cat to an acute infection. Three days later, the woman’s own temperature shot up, but she still went to her job at a day-care center. The fever worsened; she developed chest pains and shortness of breath. Two days later she drove herself to the hospital. The diagnosis was pneumonia, and she was treated with tetracycline. Shortly afterward the woman died.
Not until four days later did anyone realize that the woman had died of plague…
….Fearing that treatment might arrive too late, doctors rushed prophylactic antibiotics to the children and staff at the day-care center.. Luckily, no one exposed to the woman fell ill.
Orent, 2001

Under the same conditions of the Middle Ages, those around the infected and caring for the sick died in large numbers and the Plague spread rapidly to hundreds more, leading to thousands and ultimately millions, yet, in our more recent era, it is thankfully a completely different story.

Of course, this then raises the question: well, the plague must have changed somehow, as we know those clever bacteria can adapt very rapidly, unlike our relatively fixed genetic code. Perhaps this wasn’t the once deadly plague? Maybe it had become tamer over the centuries? This very question has recently been answered by extracting DNA from the original once deadly Plague:

Black Death? Rats and fleas finally in the clear’ Discovery Magazine

By extracting the DNA of the disease bacterium, Yersinia pestis,.. [T]o their surprise, the 14th-century strain, the cause of the most lethal catastrophe in recorded history, was no more virulent than today’s disease. The DNA codes were an almost perfect match…
Thorpe, 2014

Just think about that for a moment. This is the same once lethal plague that once killed millions some few hundred years previously and now, even if some mad terrorists release it into the public, we might not even notice that it is the pneumonic form of the Plague at all as no one would have black bubonic type lumps to say otherwise. Of course, this is really good news for most of us – I am sure we wouldn’t all escape, but we simply shouldn’t worry too much about such an event in our day and age.

However, it still doesn’t explain how we became so resistant to such previously deadly contagions like the Plague in the first place, and especially, because it hasn’t changed (genetically speaking) one jot since its devastation of the Middle Ages. A clue lies in the following excerpt.

Scientific America

How Black Death Kept Its Genes but Lost Its Killing Power

The newly sequenced genome of the plague-causing bacterium Yersinia pestis suggests human adaptations are what have kept this disease in check… The global population has likely built up some immunity from centuries of exposure to the pathogen.
Harmon, 2011 ‘How Black Death Kept Its Genes but Lost Its Killing Power’ [Video], 

Seemingly we have become immune over the centuries and the mechanism may lie in a very unlikely source: another friendlier pathogen in the form of some familiar viral characters that most of us have had some experience with over the generations. This is where Chickenpox and its relatives come into the saga of explaining whatever happened to the Plague per se.

For instance, recent molecular studies have revealed something rather surprising about the fate of the once much more lethal Plague. In essence, scientists are now finding that if mice can combat the deadly form of the PLAGUE with common viruses most of us are already infected with, it is quite possible and highly likely, that we do the same.

The Good Thing About Herpes

     The herpes family of viruses can have a surprising upside–it can protect against the bubonic plague and other bacterial contagions, at least in mice. …Nearly all humans become infected with multiple herpes virus family members during childhood. These germs not only include the herpes simplex viruses, which lead to cold sores and possibly genital herpes, but also the diseases responsible for chickenpox and “mono,” as well as several less well-known ailments. Herpes infections have bedeviled animals for more than 100 million years…
…The scientists discovered latent infections with these viruses could protect mice from bacterial infections, including Yersinia pestis, which causes bubonic plague… findings detailed in the May 17 issue of the journal Nature. The herpes viruses spur the immune system to boost levels of a protein hormone called interferon gamma “that in effect puts some immune system soldiers on yellow alert, causing them to patrol for invaders with their eyes wide open and defense weapons ready,” Virgin said. As a result, the bacteria grew more slowly and were less likely to kill the mice.
Choi, 2007

The Herpes family of viruses are, as noted above, very common and most of us already have these living inside us. Essentially, it looks like the host (that’s us) learns to defend itself making it impossible for critters to continue their destruction and it does this by slowing down the virus’ s ability to replicate in the highjacked cells and stave off the worst effects of the bacterial Plague, giving our own immune systems time to respond. The more the immune system does this: the more efficient it becomes and it does this, apparently, via the boosting of our immunity through simple exposure to things such as Chickenpox.

Basically, the Plague bacteria have to adapt or suffer the consequences of our mighty defence. They usually learn to behave themselves and become less invasive and quite tame. This immunity comes essentially from allowing the typically benign childhood disease of Chickenpox, for example, to circulate naturally so that all ages keep boosting their immune systems as you will see in the article below.

As Chickenpox is part of this family that seems to be implemented in the reason why we no longer are dying in our millions from the plague, it may be important to keep it around as it now appears that it is quite important to let it circulate naturally for the reasons outlined below. The article relates to the fact that the UK is considering introducing a vaccine into the childhood schedule to tackle Chickenpox and looking to the experience in the U.S. where the vaccine has been included in the infant and childhood schedule for some time now. The situation in Ireland is somewhat similar to that of the UK as we have never had a routine vaccine given for Chickenpox.

Chickenpox, chickenpox vaccination, and shingles

Chickenpox in the United Kingdom, where vaccination is not undertaken, has had a stable epidemiology for decades and is a routine childhood illness. Because of vaccination, chickenpox is now a rarity in the USA. In the UK vaccination is not done because introduction of a routine childhood vaccination might drive up the age at which those who are non‐immune get the illness (chickenpox tends to be more severe the older you are), and the incidence of shingles may increase. The United Kingdom is waiting to see what happens in countries where vaccination is routine.
…We know that exposure to chickenpox can significantly prevent or delay shingles (by … boosting of immunity)… Increased annual chickenpox rates in children under 5 are associated with reduced shingles in the 15–44 age group. Having a child in the household reduced the risk of shingles for about 20 years, the more contact with children the better, and general practitioners and paediatricians have a statistically significant lowering of risk,.. possibly because of their contact with sick children (teachers did not have a significantly reduced rate)…
If there is less chickenpox in children then there will be no boosting of immunity by exposure to chickenpox for middle and older aged people and thus there will be more shingles, at least until all the elderly have been vaccinated as children but this assumes that immunity conferred by vaccination is lifelong… The greater the chickenpox vaccination rates the higher the initial incidence of shingles would be until everyone was vaccinated (in other words until those of us my age who harbour varicella zoster virus in our nervous ganglia die off). It may be that a less than 100% cover by vaccination might reduce the combined chickenpox and shingles morbidity by allowing the virus to circulate in the population with only minor increases in the age of chickenpox while boosting immunity to shingles…
The extent of decline in vaccination induced immunity to chickenpox over future years is not, of course, known and neither is the proportion of those vaccinated in the USA from 1995 that will become susceptible to “geriatric chickenpox.”
Welsby, 2006, 351-52 


Remember that, based upon the above evidence, all in all, it now appears that no amount of capturing rats and cleaning up flea infestations would have helped reduce the death toll of the disease even in our modern era, as the evidence now strongly supports the black rat’s innocence – along with their flea companions – in being the harbingers of death and destruction during the Middle Ages.

Furthermore, our medical interventions cannot account for the rapid decline of deaths in such a short space of time in most regions as we never had a vaccine to try to eradicate the disease or antibiotics back then. And I don’t think the plague doctors going around with prodding sticks and bird mask with beak filled with herbs and poisons did anything other than protecting them against getting the disease itself – if it protected them at all – we don’t know. Seemingly, the plague resolved itself naturally as there are still cases in parts of the U.S. annually that typically don’t end in death and their contacts are not falling down in their millions after going: “A Tishoo…A Tishoo…” thinking it was a bad cold or the flu that turned to a case of pneumonia.

It looks like Nature has tamed this once much more deadly beast which – although it is the same disease as that of the Middle Ages (genetically speaking) that once killed millions, in more modern times via our exposure to natural viral infections with the Herpes Family over many generations  our defences against the Plague have gotten fairly robust. This seems a reasonable trade-off as it beats having the Plague compared to providing a home for something as benign (for the most part) as cold sores (just don’t go kissing any new-born infants), or childhood Chickenpox.

Perhaps, therefore, we are very fortunate here in Ireland and indeed, the UK and the other regions in Europe where they do not currently have the Chickenpox vaccine along with several boosters in the childhood schedule, as most children still  get the disease naturally, gaining life-long immunity (which is incredibly long compared to the much more variable and significantly shorter immunity we now know that all vaccines studied can offer).

Exposure to the real Herpes Family disease seems a much more beneficial option all round, as having something like Chickenpox, not only seemingly boosts natural resistance to the potential latent virus eruption later in life in the form of fairly painful Shingles but, by allowing the disease to circulate naturally, we also expose children at the appropriate age – thus reducing complications and confer life-long immunity against ever having Chickenpox again. Perhaps, of greatest importance, we may be most fortunate in allowing the Herpes Family of viruses, (of which Chickenpox is one member) to circulate naturally as it seems to be doing a fairly good job at keeping the more lethal impact of the Plague at bay.

So, if the Plague does escape from the lab again, as it has done on a number of cases in the past, try to find some children having a pox party and see if they’ll let you in.

Next week: Part Three: The Many ‘Typhoid Marys’.

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 Two

[1] James, T. (2011) Black Death: The lasting impact, BBC, (17th Feb, 2011).[Available online at]

[2] Dwyer, F (2016) 1900: Ireland’s last bubonic plague scare (5th Jan, 2016), Irish History Podcast [Available online from]

[3] Thorpe, V. (2014) Black Death? Rats and fleas finally in the clear, (30th March 2014). [Available online at],

[4] Thorpe, V. (2014) Black Death? Rats and fleas finally in the clear, (30th March 2014). [Available online at],

[5] Bugl, P (2008) History of Epidemics and Plagues’ p.8. [Available online at as PDF]]

[6] Kool, J.L., and Robert A. Weinstein R.A (2005) Risk of Person-to-Person Transmission of Pneumonic Plague, Clinical Infectious Diseases, Vol.40, Issue 8, (15 April 2005), Pp. 1166–1172, [Available online ]

[7] Stedman’s Medical Dictionary (2002) Definition of ‘hematogenous’,  American Heritage, Houghton Mifflin Company, U.S.A. [Available online at Link]

[8] Kelly, M. (2001) Unheard-of Mortality….The Black Death in Ireland, History Ireland: Issue 4 (Winter 2001), Medieval History (pre-1500), Vol. 9, [Available onlin at]

[9] James, T. (2011) Black Death: The lasting impact, BBC, (17th Feb, 2011) [Available online at]

[10] Findwyer (2016) 1900: Ireland’s last bubonic plague scare (5th Jan, 2016), Irish History Podcast [Available online from]

[11] Orent, W. (2001), Will the Black Death Return?, Discover Magazine, (1st Nov, 2001), [Available online at]

[12] Thorpe, V. (2014) Black Death? Rats and fleas finally in the clear, (30th March 2014). [Available online at],

[13] Harmon, K (2011), How Black Death Kept Its Genes but Lost Its Killing Power, Scientific America, (12th Oct. 2011), [Available online at Video]

[14] Choi, C.Q. (2007) The Good Thing About Herpes, Live Science (16th May 2007), [Available online from livescience]

[15] Welsby, P. D. (2006). Chickenpox, chickenpox vaccination, and shingles. Postgraduate Medical Journal, Vol. 82, [967], pp. 351–352. [Available online].


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