By Patrick Hunt –
Historians know disease often stalks armies in history.  The specter of invisible pathogens haunting ancient warfare may have at times seemed instead like a punitive deity taking sides. Sometimes it’s merely a much simpler question of contagion and the inability to protect against it.
While there is insufficient documentation to sort out this question in the biblical narratives of II Chronicles 32, II Kings 18-20 and Isaiah 22 & 36, these texts dovetail variously in the siege of Jerusalem by the Assyrian king Sennacherib, especially in the invasion preparations of the Judean king Hezekiah, and the massive death toll experienced by Sennacherib as recorded in these biblical passages. The account of many thousands of soldiers suddenly dying in one night by the hand of the “Angel of the Lord” appears to be supernatural hyperbole, but perhaps there is also a more natural explanation for the sudden catastrophic demise of an invading force. While we have no epidemiological evidence for this event, these literary texts of II Chronicles 32 and II Kings 18 may reveal some compelling suggestions for what may have easily happened.
Comparisons may be readily found elsewhere. Historical biopsy aside, the Assyrian invasion and siege of Jerusalem datable to 701 BCE wouldn’t be the first or last time a wartime population was decimated by plague or disease, as Thucydides recounts in 430 BCE (although plague returned several times in the ensuing few years) with the movements of armies:
“Not many days after their arrival in Attica the plague first began to show itself among the Athenians. It was said that it had broken out in many places previously in the neighborhood of Lemnos and elsewhere; but a pestilence of such extent and mortality was nowhere remembered. Neither were the physicians at first of any service, ignorant as they were of the proper way to treat it, but they died themselves the most thickly, as they visited the sick most often; nor did any human art succeed any better. Supplications in the temples, divinations, and so forth were found equally futile, till the overwhelming nature of the disaster at last put a stop to them altogether….All the birds and beasts that prey upon human bodies, either abstained from touching them (though there were many lying unburied), or died after tasting them. In proof of this, it was noticed that birds of this kind actually disappeared; they were not about the bodies, or indeed to be seen at all….the catastrophe was so overwhelming that men, not knowing what would happen next to them, became indifferent to every rule of religion or law.” 
Although the debate continues regarding the exact agent of plague that struck Athens – with archaeological evidence of sudden mass graves of at least 1000 people – there is little argument that it was pandemic. At least one historian has addressed such events:
“Infectious diseases put an end to the Golden Age of Athens, wrecked Justinian’s dream of restoring the Roman Empire to its former glory.” 
According to both II Chronicles 32:5, and Isaiah 22:10 , Hezekiah prepared for the Assyrian invasion by multiple actions, including strengthening the walls of Jerusalem – at least one wall found and securely dated by archaeological research and now known as “Avigad’s Wall” (visited by this author in 1984 and still visible in the Jewish Quarter).  Related in II Chronicles 32:3-4, II Kings 20 and Isaiah 22:11, Hezekiah also made proactive hydrological measures to restrict Assyrian access to flowing water by blocking the flowing springs external to the city and also cutting a rock conduit underground that collected the water resources within the city. Known today as the “Siloam Tunnel” (which this author also walked through from the Gihon Spring to the Siloam Pool in 1985) and arguably dated – note the claims and counterclaims in the footnote here – by its inscription ostensibly to the end of the 8th c. BCE in Hezekiah’s time,  this karstic channel protected the city by keeping the Gihon spring from flowing out into the Kidron Valley and instead brought it back underground through the limestone into the lower city now safely within the new wall.
Blocking the springs around Jerusalem – possibly by a mass effort of filling up with rocket and soil – would create a huge water crisis for the Assyrian invading force besieging the city, since armies needed a consistent large drinking source for themselves and their animals – as II Chronicles 32:3-4 notes:
“He [Hezekiah] planned with his officers and his warriors to stop the flow of the springs that were outside the city; and they helped him. A great many people were gathered, and they stopped all the springs and the wadi that flowed through the land, saying, “Why should the Assyrian kings come and find water in abundance?”
Limiting access to fresh water would be advantageous for the city under siege – especially if their own water sources were protected as noted above – and extremely disadvantageous for the invaders the longer a siege lasted. If sufficient water could not be obtained or whatever limited water was contaminated, the specter of pathogens and dehydration is multiplied immensely. One such agent of plague death – a metaphor for “the Angel of the Lord”? – is the known vector of rapidly multiplying cholera spread by the bacteria Vibrio cholera through infected water, especially if rehydration with fresh water was not possible for the same reason of blocked water sources.
When good, clean water is not easily available, after drinking fecally-contaminated water, large demographic sectors for centuries across the world – recorded in urban London, India, China, among others – have been quickly incapacitated and often decimated as cholera can kill within hours of contamination if untreated. This is confirmed in modern accounts from both the 19th through 20th and 21st centuries in wartime contamination.  According to the Mayo Clinic, cholera causes severe dehydration with up to 6.33 gallons (24 liters) of water loss per diem – or water loss of a liter per hour – with a following drop in blood pressure and debilitating cramps. Critical mass bacterial incubation after exposure can be as quick as 12 hours.  Typically cholera morbidity in modern times has been estimated at 20% of infected hosts but can be much higher depending on cramped quarters, shared water and food resources, lack of hygiene and no remediation.  The II Kings 19:35 account specifies 185,000 Assyrians died that night whereas the II Chronicles 32:21 account merely notes massive deaths of the army: “The LORD sent an angel who cut off all the mighty warriors, commanders and officers in the camp of the king of Assyria.”
For an extra-biblical account, Sennacherib’s Prism (Oriental Institute, Chicago, also British Museum copy) doesn’t record the death of his army but merely that his siege of Jerusalem was unsuccessful by extrapolation: he does not claim victory but only that he “shut up Hezekiah like a bird in a cage”.
While this author is not the first to connect pathogens and especially cholera to this Sennacherib invasion event of 701 BCE,  his ample development of the idea here follows his other paleopathology discussion[s] of ancient world army decimation.  However conjectural, assuming the biblical accounts are recording actual events – certainly not contradicted by the Assyrian cuneiform versions including Sennacherib’s Prism – cholera or a similar pathogen makes immediate sense as the natural background for the “supernatural” decimation of Sennacherib’s army and subsequent return to Nineveh without a successful siege of Jerusalem.
 Bernard Rostker. Providing for the Casualties of War, Rand Corporation, 2013, ch. 9, 241: “From the time of the Greeks…just being a soldier was an open invitation to death from the countless communicable diseases that were the scourge of military camps.”
 Thucydides, Peloponnesian War, 2.47.3-4, 50.1, 52.3
 R. S. Bray. Armies of Pestilence: The Impact of Disease on History. Barnes and Noble reprint, 1996, intro. Also see William Rosen, Justinian’s Flea: The First Great Plague and the End of the Roman Empire, Penguin, 2008, for a popular application of the Constantinople plague information provided by Procopius in his Sectet History. mid-6th c. CE.
 M. Broshi. “The Expansion of Jerusalem in the Reigns of Hezekiah and Manessah.” Israel Exploration Journal 24.1 (1974) 21-6, note p. 21.
 A. E. Shimron and A. Frumkin, “The Why How and When of the Siloam Tunnel Reevaluated: A Reply,” Bulletin of the American Schools of Oriental Research 364 (2011) 53-60 (this article challenges the geology of the Sneh, Weinberger, and Shalev article of the same name and same journal (BASOR 359 of 2010); G. A. Rendsburg and W. M. Schniedewind, “The Siloam Tunnel Inscription: Historical and Linguistic Perspectives,” Israel Exploration Journal 60 (2010) 188-203 (note the more compelling arguments for it being Hezekiah’s construction); M. K. Y. H. Hom. “Where Art Thou, O Hezekiah’s Tunnel…[Waterworks]” Journal of Biblical Literature 135.3 (2016) 493-503. Note in above Rendsburg and Schniedewind 2010 citation, footnote 1, p. 188: “While there is no absolute proof that the Siloam Tunnel is the tunnel attributed to King Hezekiah in the biblical sources, with no evidence to the contrary (especially in light of other studies cited herein), our standpoint is that they are one and the same.”
 J. Glenn Morris, “Cholera: Modern Pandemic Disease of Ancient Lineage” Emerging Infectious Diseases vol. 17 (11) November, 2011, 2099-2104; “Cholera: Key Facts”, World Health Organization January 17, 2019 (https://www.who.int/news-room/fact-sheets/detail/cholera).
 Remy Melina, “How Does Cholera Kill?” Live Science, October 22, 2010, quoting Mayo Clinic staff and Jason Harris, Massachusetts General Hospital, (https://www.livescience.com/10212-cholera-kill.html).
 E. J. Nelson, J. B. Harris, J. Glenn Morris. S. B. Calderwood, A. Camilli. “Cholera Transmission: the Host, pathogen and bacteriophage dynamic.” Nature Reviews Microbiology 7 (2009) 693-702 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3842031/); E. K. Lipp, A. Huq, R. R. Colwell. “Effects of global climate on in factious disease: the cholera model.” Clinical Microbiology Reviews 15.4 (2002) 757-70 (https://www.ncbi.nlm.nih.gov/pubmed/12364378/)
.  In his New Oxford Annotated Bible commentary p. 566 on II Kings 19:35-36, Iain Provan notes “some commentators suggest that nature causes, such as plague, may lie behind the reference to the action of the angel of the LORD.” The “angel of the LORD” also reminds of the plague of the first-born in Egypt in Exodus 12:29-30 although there it is the LORD as agent of death. Note John Bright, A History of Israel, Westminster/John Knox Press, 2000 ed., 24 & ff. discusses plague in this event as does eminent historian William H. Macneill in his essay in the collection What If? (The World’s Foremost Military Historians Imagine What Might Have Been) G. P. Putnam’s Sons, 1999.
 Patrick Hunt and Andreaa Seicean. “Alpine Archaeology and Paleopathology: Was Hannibal’s Army also decimated by epidemic while crossing the Alps?” Archaeolog (Stanford) May 20, 2007. https://web.stanford.edu/dept/archaeology/cgi-bin/archaeolog/?p=123