boris.earth

How many people died of the plague? (draft)

One of the first queries that comes up when you google "how many people died of", is how many people died of the (black) plague. Unfortunately, pretty much every answer that you can find online is wrong.

Google Suggest top hits - how many people died of
300 years after plague died out in Europe, it is still heavily present in people's mind

You will get plenty of answers when you search for the death toll of plague - there are answers on Wikipedia and on Encyclopedia Britannica. There are nice visualizations made by the National Geographic and the Visual Capitalist, and many books or scientific publication on plague will list a death toll somewhere in their introduction.


But they are all wrong, in one of these two ways:

  1. Most websites are just parroting each other's random numbers (BBC, Reuters, etc), and then get cited by Wikipedia as a credible source1.
  2. The most commonly returned answer by search engines is specific to the 1346-1351 Black Death epidemic in Europe. That is not the question that we asked!

So, let's see how far we can get in answering how many people died of the plague.

The Time before the Three Plague PandemicsπŸ”—

The first thing you need to know is that plague has been killing people for at least 5,000 years2. And when you move that far back in history it becomes extremely difficult to assess how many people lived, let alone how many people died of a particular disease. However, it does look like that 5,000 years ago plague was already wrecking havock: remnants of the plague bacterium have been found across Eurasia3, in a surprising large fraction (like 2.5%) of the corpses that were tested for the presence of ancient plague DNA.

A map of ancient plague findings, predating the known pandemics
Plague has been recovered from human remains for at least 5,000 years (compiled from literature)

If it turns out to be a reasonable assumption that 2.5% of all people that lived between 3000BC and 541AD died of the plague, then we can leverage demography datasets like (https://easy.dans.knaw.nl/ui/datasets/id/easy-dataset:74467)[HYDE 3.2], and birth rate estimates of 80 per 1,000 before CE and 60 per 1,000 until 1750CE used in (https://www.prb.org/articles/how-many-people-have-ever-lived-on-earth/)[this blog post] to get to a total number of people that died of plague. One difficulty is to extrapolate the above map to the full range across which plague was common. And whether you pick a narrow range of countries in which plague existed for 3,500 years, or a broader range of countries is going to matter a lot for any total estimate of plague deaths pre-pandemic.

For now, I picked all the countries in Eurasia west of the China-India axis - excluding China and India for now, until more evidence comes from those places. I included the countries in Africa that border the Mediterranean, as that coastline has long been connected to Europe. I also included a group of countries in Central Africa, because an analysis of the plague strains that persist until today in those countries suggests that plague has been there for at least 3,000 years (now that current-day plague strains have been tentatively linked to the "Angola" strain that lies very deep into plague's phylogenetic tree)4. You can look at an image of this range here.

If you take this geographic range, and run the numbers, you will get as a rough approximation that 222.1 million people died of plague between 3000BC and 541AD. But if you take a narrower range of countries (like here)), the estimate is 98.2 million.

CAVEATS: There is a huge range of uncertainty in this estimate, coming in particular from the following four points.

  • I used the baseline population estimates from HYDE, but HYDE provides a low and a high range
  • I assumed a constant share of 2.5% all-cause mortality by the plague, and that share of all-cause mortality is based on the ratio of positive plague samples found in a small sample of corpses tested for plague. UPDATE THIS NUMBER
  • The assumed geographic extent of the plague for this 3,500 year period matters a lot - for two geographic ranges, I have an estimate of 98.2 to 222.1 million deaths.
  • We known nearly nothing about plague in the time before 5,000 BCE. As far as we can tell, plague and its sibling species of Yersinia pseudotuberculosis diverged into two species somewhere between 34,659–78,803 years ago 3, which means there might have been 70,000 years of plague preceding our estimate here.

The First Plague PandemicπŸ”—

Fast forward to the year 541 AD in Pelusium, Egypt. The outbreak recorded in the historic records in Pelusium is typically considered the start of the First Plague Pandemic, which lasted until 750 AD. The plague spread across Europe, and DNA of the plague bacterium has been recovered from dozens of sites, confirming that this was indeed a plague pandemic5,6. The plague may have well spread into Africa and Central Asia as well - we just have very little information about what happened outside of Europe.

There is a very lively scientific discussion ongoing on how deadly this first plague pandemic actually was7,8, and it is worth reading both sides to get a feeling for the challenges of tallying up the dead in historic times.

The upper range is at the 15-100 million people in those 250 years, when you limited the counting to just Europe. EXPAND

In between the First Two PandemicsπŸ”—

If you somehow succeeded in tackling the challenges of enumerating the dead from prehistoric plague outbreaks and from the First Plague Pandemic, be mindful that you do not skip over the period between the end of the First Pandemic in 750 AD and the traditional start of the Second Pandemic in 1346 AD9.

It has been something of an entrenched idea that the Black Death was the start of the Second Plague Pandemic, which means that outbreaks between 750 AD and 1346 AD were not considered in the context of possibly being plague. That idea is changing now with a recent publication on plague in Baghdad, Iraq in 1258 AD10, and it wouldn't do to forget those places in an accurate tally of the total death toll of the plague.

But the period is in between the pandemics, so perhaps we should assume a lower all-cause mortality that during pandemic times. I have a very shaky estimate of 1.5% for the all-cause mortality during the second plague pandemic, so we should probably go for a lower number in between the pandemics. And perhaps we should scale back the geographic range as well - even though plague outbreaks might have continued to occur in the Middle East, I would be surprised if plague was as prevalent as during the First or Second Plague Pandemic in Europe, and everyone failed to notice that.

The Second Plague PandemicπŸ”—

The Second Plague Pandemic was fairly brutal. Besides wiping out half of Europe to start with (the usual estimate is 30-60%), the disease also kept recurring at lower city-wide mortality levels. Common pattern for urban areas are visible in Haarlem (Davis), which is still comparable to (the uncommonly large) London - as in every 40 years a 20% mortality crisis, and every 3-4 years a 5% crisis. That tallies up to a 1.5% all-case mortality.

That would be a full % lower than the 2.5% all-case mortality that was our rough estimate for pre-pandemic plague.

In between the Second and Third PandemicsπŸ”—

When did the Second Plague Pandemic end? The outbreaks that are typically considered to represent the end of the Second Pandemic (the plague of Marseille in 1720-1722 or the plague in Moscow in 1770-1772), are only so from a rather narrow western-Europe perspective.

When you take older compendiums of plague, such as that of Georg Sticker 11, you will find records of (presumably) plague present from Eastern Europe to India between 1723 to 1893. With the Third plague pandemic starting in Southwest China in 1788 or 1855, depending on who you ask, there is actually an overlap between the end of the Second and the start of the Third pandemic.

Plague in Central Asia in between the Second and Third Plague Pandemic
Plague in Central Asia in between the Second and Third Plague Pandemic

The Third Plague PandemicπŸ”—

The Third Pandemic can best be split up continent by continent, as different continents had very different death tolls ([see my guest post on lrhmatters.com])(https://lrhmatters.com/drivers-of-health/the-virtual-eradication-of-plague).

Making the roughest of estimates, we can say that by far the largest death-toll was in India and Southern China, for a total of about 21 million people.

After the Third Pandemic.πŸ”—

There is not really a well-defined end of the Third Pandemic, but looking at various papers from different continents (Bramanti, Kuguler, Sun, Neerincxk, Jones), plague stopped being an epidemic disease around the 1950's, with case numbers returning globally to close to 0. Plague kept flaring up in outbreaks spilling over from local wildlife reservoirs after the '50s, but there is nothing that signals that plague was still spreading by human agency, like it did during the pandemics.

WHO used to have a dataset online of plague cases per year and per country, but no longer so. So I compiled the summary reports published by the WHO, to get a total (reported!) number of cases and deaths from 1954 until 2018. These reports contain some copy-paste errors and typos (the totals in the report seem to have been added up by hand, and sometimes a row is shifted one entry), but by browsing the WER archives and by doing some comparative work between WER reports, I removed most of these errors. You can download the excel file here.

The global total for the period of 65 years from 1954 to 2018 sums up to 1,149,952 cases and 9874 deaths, or about 150 deaths per year.

How many people died of the Black Plague?πŸ”—

From the incomplete calculations above, we can see that plague from 1850 onwards killed in the region of 21 million people. We also have a shaky estimate for the time period from 3,000 BC to 750 AC of somewhere in the region of 270 million people.

That leaves the period of 750 AC to 1850 AC. I will keep you waiting a little longer, while I update the numbers and the methodology until I have at least something of an estimate.

FootnotesπŸ”—

1

obligatory XKCD comic: 'citogenesis'

2

Andrades ValtueΓ±a et al. (2017) β€˜The Stone Age Plague and Its Persistence in Eurasia’, Current biology: CB, 27(23), pp. 3683–3691.e8.

3

Rasmussen, S. et al. (2015) β€˜Early Divergent Strains of Yersinia pestis in Eurasia 5,000 Years Ago’, Cell, 163(3), pp. 571–582.

12

Leulmi, H. et al. (2014) β€˜Detection of Rickettsia felis, Rickettsia typhi, Bartonella Species and Yersinia pestis in Fleas (Siphonaptera) from Africa’, PLoS neglected tropical diseases, 8(10), p. e3152.

5

Wagner, D.M. et al. (2014) β€˜Yersinia pestis and the Plague of Justinian 541–543 AD: a genomic analysis’, The Lancet infectious diseases, 14(4), pp. 319–326.

6

Keller, M. et al. (2019) β€˜Ancient Yersinia pestis genomes from across Western Europe reveal early diversification during the First Pandemic (541-750)’, Proceedings of the National Academy of Sciences of the United States of America, 116(25), pp. 12363–12372.

7

Mordechai, L. et al. (2019) β€˜The Justinianic Plague: An inconsequential pandemic?’, Proceedings of the National Academy of Sciences of the United States of America, 116(51), pp. 25546–25554.

8

Sarris, P. (2022) β€˜New Approaches to the β€œPlague of Justinian’, Past & present, 254(1), pp. 315–346.

9

Barker, H. (2021) β€˜Laying the Corpses to Rest: Grain, Embargoes, and Yersinia pestis in the Black Sea, 1346–48’, Speculum, 96(1), pp. 97–126.

10

Fancy, N. and Green, M.H. (2021) β€˜Plague and the Fall of Baghdad (1258)’, Medical history, 65(2), pp. 157–177.

13

Krauer, F. and Schmid, B.V. (2021) β€˜Mapping the plague through natural language processing’, medRxiv Preprint.