Contagion & Quarantine

Long before anyone could say what passed between the sick and the well, cities acted as though something did. They shut the leper outside the wall, held the ship at anchor, counted out a span of days and called the count a law. The number they fixed upon, forty, owed more to Scripture and to Hippocrates than to any measured contagion, and it happened to be right. This is the story of a practice that ran six centuries ahead of its reason: of the physicians who argued from the evidence of their own eyes that disease could travel, of the one who was strangled for pressing the point too hard, and of the sealed rooms I still darken today for a cause we have understood only in the last of those centuries.

The seed in the Canon

The book this plate follows, the Canon of Medicine that Ibn Sīnā finished around 1025, carried the idea in plain words. In the chapters on the wasting of the lung he set down that phthisis, the consumption, travels from the sick to the sound; that corruption may be carried in water and in the soil; and that a physician should keep the consumptive apart from the well.¹ From those few lines a large and much-loved modern story has grown, that Avicenna invented quarantine, that he fixed its length at forty days and gave it a name, al-arbaʿiniya, the forty.²

The first half of the story is nearly true and the second very nearly a fiction. The Canon urges isolation; it does not build the forty-day detention that the word quarantine now means, and the number belongs to a later world and another faith. Even the historians most eager to hand Avicenna the credit concede that it is not clear Europe ever learned its quarantine from his book at all.³ What the Canon held was the seed: the bare claim that contagion is real and the afflicted should be set aside. The institution, and the arithmetic, other hands would build, and they would build them against harder resistance than a physician writing quietly at his desk ever met.

A word the law forbade

To say that disease passed from one body to another was, in the medieval Islamic world, to step onto contested ground. A saying of the Prophet, preserved in the most trusted collections, was flat: lā ʿadwā, there is no contagion.⁴ The objection was not medical but doctrinal. To grant a fever the power to sicken whomever it touched, by its own nature, was to forget that nothing in creation acts of itself, that health and sickness alike come only by the will of God. Yet the same body of tradition held sayings that pulled the other way, and hard: flee the leper as you would flee the lion; when you hear the plague is in a land do not enter it, and if it breaks out where you stand do not flee.⁵

The orthodox squared the two by ruling that disease was real in its spreading but not sovereign in it. It passed, when it passed, because God willed the passing, not because the illness owned any power to compel. It was a careful settlement, and it left a narrow path for the physician. He might act against contagion, might shut a door or keep his distance, so long as he did not claim the contagion acted on its own. To reason too plainly from what he saw at the bedside, to let the evidence of the disease speak louder than the received word about it, was to risk being told he had made a small second god out of a sickness.

The evidence of the senses

The Black Death gave the argument its witnesses. When the pestilence reached Granada in 1348 and carried off, past any reliable counting, a great part of the city, two physicians of al-Andalus sat down to write what they had watched.⁶ At Almería, ʿAlī ibn Khātima recorded the epidemic almost house by house. At Granada, the vizier and polymath Lisān al-Dīn ibn al-Khaṭīb wrote a short treatise whose most famous passage steps straight across the fence. The existence of contagion, he argued, is proved by experience and investigation, by what the senses observe and what trustworthy witnesses report; it shows itself in the carrying of the sickness by a garment, a vessel, even an earring, in its spread from a house to those who visit it, in the plain fact that those who shut themselves away came through while those who mingled with the sick did not.⁷

Then the argument that would cost him. Where a report handed down from tradition contradicts what the eye has plainly seen, he held, the tradition must be read allegorically rather than pressed against the evidence; contagion was a matter, in the end, for the physician and not the jurist.⁸ Ibn Khātima, more cautiously, granted much the same evidence of contagion and then, in almost the next breath, went on explaining the plague by the old miasma, the corrupt vapour breathed out by the dying. The two accounts, contagion and bad air, lived side by side in one careful mind, because neither man could yet say what the thing was that travelled.⁹

What became of Ibn al-Khaṭīb is the darker half of the page. Two decades later he fell, as viziers fell, in the machinery of court politics between Granada and the Marīnid sultanate of Fez. He was imprisoned, tried for zandaqa, unbelief, and strangled in his cell one night in 1374 before the council of scholars could return a verdict; his body was dug up afterward and burned.¹⁰ The charges were political before they were doctrinal. But among the heresies his enemies gathered against him stood exactly this: that he had set the evidence of the senses above the received word, on the very matter of contagion.¹¹ The argument from what the eyes could see had, in the end, to be defended with a life, and in his case it lost.

Thirty days, then forty

Contagion won as practice long before it won as theory, and it won first not in a treatise but in a harbour. In 1377 the city of Ragusa, the Adriatic port now called Dubrovnik, ruled that travellers arriving from places where the plague was abroad must wait in an appointed spot, apart, before they were let in: thirty days, a trentino.¹² Other cities took up the measure and stretched it to forty, a quarantino, and it is the longer count whose Italian name, quaranta, forty, has ridden in every European language since as quarantine.¹³ Venice built the thing in stone, setting its held ships and their crews on a lagoon island beside the church of Santa Maria di Nazareth; the island's name blurred, by way of Nazaretto and the lazzaretto it came to resemble, into the common word for a plague-house across the continent, and carried folded inside it the older Lazarus of the lazar-house, the leprous whom Scripture had already taught the West to lodge outside the gate.¹⁴

Why forty, and not thirty, or fifty? No one wrote the reason down, and the likeliest answer is that the number was chosen because it was already heavy with meaning. The Hippocratic writers had taught that an acute disease declares itself, for life or death, within forty days; the Pythagoreans had made forty a figure of completion; and Scripture had rained on the earth for forty days, kept Moses on the mountain and Christ in the wilderness for forty each, and counted forty for the fast of Lent.¹⁵ The physicians of the plague reached for a span their whole culture already read as the full length of a trial or a cleansing, and it happened, by a good luck they had no way of knowing they were having, to run longer than the days a plague needs to declare itself or to burn out inside a shut house. They were right about the interval for reasons that had nothing to do with why it was right.

They were also wrong about the cause the entire time they practised the cure. The same cities that held the ship at anchor lit fires in the streets and pressed herbs and vinegar to the face, because the reigning explanation, from Galen down, was still the miasma, the poisoned air; the beaked mask of the later plague doctor was a nosegay built for the whole head, its long bill packed with aromatics against a stench.¹⁶ Quarantine was a contagionist act carried out, for five hundred years, by people who mostly believed in bad air, and it went on working regardless. Only in the nineteenth century did the reason arrive to fit the ritual, when John Snow traced cholera to a single pump, and Pasteur's flasks and Koch's stained bacillus at last named the thing that had been riding in the garments and the vessels all along, exactly where the senses of a strangled man had placed it five centuries before.¹⁷

Read from the Ward

There is a room on my unit with a door that seals, and a soft mechanical sigh when it does. The air inside is held a little below the pressure of the corridor, so that when the door opens nothing drifts outward; we gown and glove and mask before we cross into it, and strip all of it off again at the threshold on the way back, in an order drilled into the hands until the mind need not attend. When I put a patient behind that door I am doing, with machinery and evidence Ibn al-Khaṭīb never had, the very thing he reasoned his way toward from the garments and the earrings: holding apart the thing that travels. The one difference, and it is the whole of the difference, is that I know what it is. I have its name, its size, the route it takes through the air. I can say aerosol where he could say only the senses.

And still I count days I cannot entirely defend. The interval a contact must wait, the span before an exposure is called safe, the number of clear days before the door may open again: some of these rest on good measurement, and some are rounded, inherited, settled by custom as much as by trial, our own quiet descendants of the forty that came out of Genesis and Hippocrates before it ever came off a ward. When the last plague circled the earth inside my own working life, we sent people home for fourteen days, and then, as the evidence shifted under us, for ten, and we argued over the number in exactly the way that tells you it was never only a measurement. It was a settlement between what we knew and what we feared, a line drawn in time on evidence that did not yet amount to proof. Quarantine has always been that line. The forty was a guess that held; my fourteen was a guess we corrected in public.

What I try to keep beside me, on the nights the sealed door does its quiet work, is the man who made the case before there was any way on earth to win it. Ibn al-Khaṭīb wrote that the evidence of the senses was the surer proof, and that the sick should be kept from the sound, and it went into the ledger of his heresies, and they strangled him in the dark and burned what was left of him by the Fez gate. The germ he could never have seen arrived five hundred years too late to save his name, and proved him right about the garments and the earrings all the same. I open the door. The pressure equalises with a breath. Inside that room is the oldest thing medicine knows how to do, which is to set the sick apart and wait, and which we did for six centuries with the wrong reason and the right result, and do now with the right reason and, on the better nights, the humility to remember which of the two we came to first.

1. Ibn Sīnā (Avicenna), al-Qānūn fī al-ṭibb (The Canon of Medicine), on the diseases of the chest and the wasting of the lung: the Canon treats pulmonary consumption (phthisis) as passing from the sick to the sound, holds that corruption may be carried by water and by soil, and advises separating the consumptive from the well. See "Reflections on Avicenna's Impact on Medicine: His Reach Beyond the Middle East," Journal of Community Hospital Internal Medicine Perspectives 10, no. 4 (2020), PMC7427450; Peter E. Pormann and Emilie Savage-Smith, Medieval Islamic Medicine (Edinburgh: Edinburgh University Press, 2007), chap. 4. These are the attributions of the modern literature on Avicenna rather than verbatim passages quoted from the Canon, and the article treats them as such. (Codex Chronica, The Canon of Medicine, Plate V.)↩
2. The widely circulated modern claim that Avicenna "invented quarantine" and fixed a forty-day isolation he named al-arbaʿiniya ("the forty") is repeated across popular and heritage sources but is not securely grounded in the text of the Canon, which recommends isolation of the consumptive without instituting a fixed forty-day term. See, for the popular attribution and its limits, "Reflections on Avicenna's Impact on Medicine," PMC7427450.↩
3. Even accounts sympathetic to the attribution grant that "it is not clear if Europe learned about quarantining from Avicenna"; the forty-day institution as Europe practised it is first documented in the Adriatic and Italian ports of the fourteenth century (see nn. 12–13). "Reflections on Avicenna's Impact on Medicine," PMC7427450; Eugenia Tognotti, "Lessons from the History of Quarantine, from Plague to Influenza A," Emerging Infectious Diseases 19, no. 2 (2013): 254–259.↩
4. Ṣaḥīḥ al-Bukhārī, Kitāb al-Ṭibb (Book of Medicine): "lā ʿadwā wa-lā ṭiyara…" ("there is no contagion, and no evil omen…"). On the theological reading, that to grant a disease power to sicken of its own nature offended the doctrine that nothing acts but by the will of God, see Justin K. Stearns, Infectious Ideas: Contagion in Premodern Islamic and Christian Thought (Baltimore: Johns Hopkins University Press, 2011), chaps. 1–2; Michael W. Dols, The Black Death in the Middle East (Princeton: Princeton University Press, 1977), chap. 4.↩
5. The counter-traditions include "flee from the leper as you would flee from a lion" and the plague-flight ḥadīth ("when you hear of it in a land, do not enter it; if it breaks out where you are, do not leave"); the Prophet is also reported to have accepted a leper's allegiance by message, without contact. On the tension among these reports and its long exegetical afterlife, see Stearns, Infectious Ideas, chaps. 1–3; Lawrence I. Conrad, "A Ninth-Century Muslim Scholar's Discussion of Contagion," in Contagion: Perspectives from Pre-Modern Societies, ed. Lawrence I. Conrad and Dominik Wujastyk (Aldershot: Ashgate, 2000).↩
6. On the arrival of the Black Death at Granada in 1348–1349 and the two Andalusī plague treatises it produced, see William B. Ober and Nabil Aloush, "The Plague at Granada, 1348–1349: Ibn al-Khatib and Ideas of Contagion," Bulletin of the New York Academy of Medicine 58, no. 4 (1982): 418–424, who caution that the mortality at Granada cannot be reliably reckoned; Dols, The Black Death in the Middle East, chap. 3.↩
7. Ibn al-Khaṭīb, Muqniʿat al-sāʾil ʿan al-maraḍ al-hāʾil, composed in the years after the 1348 plague (dated variously c. 1349–1362). Ober and Aloush render the key passage: that infection exists "is confirmed by experience, investigation, insight, personal observation, and reliable reports. These are the elements of proof," with the sickness carried by garment, vessel and earring and passing from a house to those who enter it; the wording paraphrased in the body follows their translation. See Ober and Aloush, "The Plague at Granada," 421–423; Stearns, Infectious Ideas, chap. 3.↩
8. Ober and Aloush translate his exegetical move directly: a proof taken from tradition, "if observation and inspection show the contrary, must be interpreted allegorically." The further characterisation of contagion as a matter for the physician rather than the jurist is the article's gloss on his empiricism. See Ober and Aloush, "The Plague at Granada," 422–423; Stearns, Infectious Ideas, chap. 3.↩
9. Ibn Khātima al-Anṣārī, Taḥṣīl gharaḍ al-qāṣid fī tafṣīl al-maraḍ al-wāfid (Almería, 1349), recognised much the same evidence of contagion yet continued to explain the epidemic largely by miasma, the corrupt vapour breathed out by the dying, the two frames coexisting in one author. See Dols, The Black Death in the Middle East, chap. 3; Stearns, Infectious Ideas, chap. 3.↩
10. Ibn al-Khaṭīb (1313–1374), vizier and polymath of Naṣrid Granada, fell in the factional politics between Granada and the Marīnid court of Fez; imprisoned and tried for zandaqa (unbelief), he was strangled in his prison cell before a verdict could be reached (Ober and Aloush, "The Plague at Granada," 420) in 776 AH / 1374, and his body was afterward disinterred and burned near the Bāb al-Maḥrūq at Fez. For the date, place and burning, which rest on the accounts deriving from his pupil Ibn Khaldūn, see Dols, The Black Death in the Middle East, chap. 3; "Ibn al-Khaṭīb, Lisān al-Dīn," Encyclopaedia of Islam, 2nd ed.↩
11. Among the doctrinal offences his enemies assembled was his rationalist handling of contagion, the claim that the evidence of the senses could override a received tradition on the matter; the proceedings, however, were driven by private and political enmities before doctrine. See Stearns, Infectious Ideas, chap. 3; Dols, The Black Death in the Middle East, chap. 3; Ober and Aloush, "The Plague at Granada," 423, noting that the charge of heresy was supplemented by accusations of malfeasance in office.↩
12. On the Ragusan measure of 1377 requiring arrivals from plague districts to pass a period apart before admission, thirty days, a trentino, see Tognotti, "Lessons from the History of Quarantine," 254–255; on its precise enactment (27 July 1377, in the Liber Viridis) see Zlata Blažina Tomić and Vesna Blažina, Expelling the Plague: The Health Office and the Implementation of Quarantine in Dubrovnik, 1377–1533 (Montreal: McGill-Queen's University Press, 2015).↩
13. On the extension of the term to forty days (quarantena) and the passage of the Italian quaranta ("forty") into the European word quarantine, see Paul S. Sehdev, "The Origin of Quarantine," Clinical Infectious Diseases 35, no. 9 (2002): 1071–1072; "Etymologia: Quarantine," Emerging Infectious Diseases 19, no. 2 (2013): 263.↩
14. On the Venetian lazaretto (from 1423, on the island of Santa Maria di Nazareth, its name passing between Nazareth and Lazarus) see Tognotti, "Lessons from the History of Quarantine," 255–256. The lazar-house and its patron St Lazarus belong to the older Western segregation of the leprous that the plague-house inherited (Leviticus 13:45–46, "he shall dwell alone; his dwelling shall be outside the camp"); see Sehdev, "The Origin of Quarantine," 1071.↩
15. The reason for forty rather than another number was not recorded; the likeliest sources are the Hippocratic doctrine that an acute disease resolves within forty days, Pythagorean number-lore, and the pervasive biblical forty (the Flood, Moses on Sinai, Christ's fast in the wilderness, and Lent). See Tognotti, "Lessons from the History of Quarantine," 255; Sehdev, "The Origin of Quarantine," 1071–1072.↩
16. Quarantine was a contagionist measure practised within a culture that still explained epidemic disease chiefly by miasma, corrupt air; the same authorities lit purifying fires and carried aromatics, and the beaked mask of the later plague doctor was a container for such aromatics against the smell. On the coexistence of contagionist and miasmatic measures, see Vivian Nutton, "The Seeds of Disease: An Explanation of Contagion and Infection from the Greeks to the Renaissance," Medical History 27, no. 1 (1983): 1–34; Tognotti, "Lessons from the History of Quarantine," 256.↩
17. Girolamo Fracastoro's seminaria contagionum (De Contagione et Contagiosis Morbis, 1546) gave contagion a theory, but miasma remained the dominant account until the nineteenth century, when the water-borne and germ demonstrations at last fitted a cause to the practice. See Nutton, "The Seeds of Disease"; and, in this series, Codex Chronica, The Broad Street Pump (Plate XVIII, John Snow, 1854), The Swan-Neck Flask (Plate XXI, Pasteur), and The Tubercle Bacillus / Koch's Postulates (Plates XXV–XXVI, Koch).↩

• Blažina Tomić, Zlata, and Vesna Blažina. Expelling the Plague: The Health Office and the Implementation of Quarantine in Dubrovnik, 1377–1533. Montreal: McGill-Queen's University Press, 2015.
• Conrad, Lawrence I. "A Ninth-Century Muslim Scholar's Discussion of Contagion." In Contagion: Perspectives from Pre-Modern Societies, edited by Lawrence I. Conrad and Dominik Wujastyk. Aldershot: Ashgate, 2000.
• Dols, Michael W. The Black Death in the Middle East. Princeton: Princeton University Press, 1977.
• "Etymologia: Quarantine." Emerging Infectious Diseases 19, no. 2 (2013): 263.
• Fracastoro, Girolamo. De Contagione et Contagiosis Morbis. Venice, 1546.
• Ibn Sīnā (Avicenna). al-Qānūn fī al-ṭibb (The Canon of Medicine). Completed c. 1025.
• Nutton, Vivian. "The Seeds of Disease: An Explanation of Contagion and Infection from the Greeks to the Renaissance." Medical History 27, no. 1 (1983): 1–34.
• Ober, William B., and Nabil Aloush. "The Plague at Granada, 1348–1349: Ibn al-Khatib and Ideas of Contagion." Bulletin of the New York Academy of Medicine 58, no. 4 (1982): 418–424.
• Pormann, Peter E., and Emilie Savage-Smith. Medieval Islamic Medicine. Edinburgh: Edinburgh University Press, 2007.
• "Reflections on Avicenna's Impact on Medicine: His Reach Beyond the Middle East." Journal of Community Hospital Internal Medicine Perspectives 10, no. 4 (2020). PMC7427450.
• Ṣaḥīḥ al-Bukhārī. Kitāb al-Ṭibb (Book of Medicine).
• Sehdev, Paul S. "The Origin of Quarantine." Clinical Infectious Diseases 35, no. 9 (2002): 1071–1072.
• Stearns, Justin K. Infectious Ideas: Contagion in Premodern Islamic and Christian Thought. Baltimore: Johns Hopkins University Press, 2011.
• Tognotti, Eugenia. "Lessons from the History of Quarantine, from Plague to Influenza A." Emerging Infectious Diseases 19, no. 2 (2013): 254–259.