A Discourse on the Plague

by Richard Mead

The third Cause we assigned for the spreading of Contagion, was a corrupted State of Air. Although the Air be in a right State, yet a sick Person may infect those who are very near him: As we find the Pestilence to continue sometimes among the Crew of a Ship, after they have sailed out of the Infectious Air wherein the Disease was first caught. A remarkable Accident of this Nature is recorded to have happened in the Plague at Genoa in the Year 1656. Eleven Persons put to Sea in a Felucca, with design to withdraw themselves from the Contagion, and retire into Provence; but one of them falling sick of the Plague soon after they had imbarked, infected the rest; insomuch that others being taken ill, and dying in their turns, they were not admitted any where, but were forced to return from whence they came: and by that time the Boat arrived again at Genoa no more than one of them survived[55].

However in this Case the Malady does not usually spread far, the contagious Particles being soon dispersed and lost. But when in a corrupt Disposition of the Air the contagious Particles meet with the subtile Parts generated by that Corruption, by uniting with them they become much more active and powerful, and likewise of a more durable Nature; so as to form an infectious Matter capable of conveying the Mischief to a greater distance from the diseased Body, out of which it was produced.

In general, a hot Air is more disposed to spread Contagion than a cold one, as no one can doubt, who considers how much all kinds of Effluvia are farther diffused in a warm Air, than in the contrary. But moreover, that State of Air, when unseasonable Moisture and want of Winds are added to its Heat, which gives birth to the Plague in some Countries, will doubtless promote it in all. For Hippocrates sets down the same Description of a Pestilential State of Air in his Country, as the Arabians do of the Constitution, which gives Rise to the Plague in Africa[56]. Mercurialis assures us the same Constitution of Air attended the Pestilence in his time at Padua[57]: and Gassendus observed the same in the Plague of Digne[58]. Besides, it is easy to shew how the Air, by the sensible ill Qualities discoursed of in the last Chapter, should favour infectious Diseases, by rendering the Body obnoxious to them.

Indeed other hurtful Qualities of the Air are more to be regarded than its Heat alone: for the Plague is sometimes stopt, while the Heat of the Season increases, upon the Emendation of the Air in other respects. At Smyrna the Plague, which is yearly carried thither by Ships, constantly ceases about the 24th of June, by the dry and clear Weather they always have at that time: the unwholsome Damps being then dissipated that annoy the Country in the Spring. However, the Heat of the Air is of so much Consequence, that if any Ship brings it in the Winter Months of November, December, January, or February, it never spreads: but if later in the Year, as in April or afterwards, it continues till the time before mentioned.

But moreover, what was said before of some latent Disorders in the Air having a share in spreading the Plague, will likewise have place in these Countries; as the last Plague in the City of London remarkably proves, the Seeds of which, upon its first Entrance, and while it was confined to a House or two, preserved themselves through a hard frosty Winter, and again put forth their malignant Quality as soon as the Warmth of the Spring gave them force: but, at the latter end of the next Winter they were suppressed so as to appear no more, though in the Month of December more than half the Parishes of the City were infected.

A corrupted State of Air is, without doubt, necessary to give these contagious Atoms their full force; for otherwise it were not easy to conceive how the Plague, when once it had seized any Place, should ever cease but with the Destruction of all the Inhabitants: Which is readily accounted for by supposing an Emendation of the Qualities of the Air, and the restoring of it to a healthful State capable of dissipating and suppressing the Malignity.

On the other hand, it does not appear, that the Air, however corrupted, is usually capable of carrying Infection to a very great distance; but that commonly the Plague is spread from Town to Town by infected Persons and Goods: for there are numberless Instances, where the Plague has caused a great Mortality in Towns, while other Towns and Villages, very near them, have been entirely free. And hence it is, that the Plague sometimes spreads from Place to Place very irregularly. Thuanus[59] speaks of a Plague in Italy, which one Year was at Trent and Verona, the next got into Venice and Padua, leaving Vicenza, an intermediate Place, untouched, though the next Year that also felt the same Stroke: a certain Proof that the Plague was not carried by the Air from Verona to Padua and Venice; for the infected Air must have tainted all in its Passage. We have had lately in France one Instance of the same Nature, when the Plague was carried at once out of Provence several Leagues into the Gevaudan. Usually indeed the Plague, especially when more violent than ordinary, spreads from infected Places into those which border upon them: which probably is sometimes effected by some little Communication infected Towns are obliged to hold with the Country about them for the sake of Necessaries, the Subtlety of the Venom now and then eluding the greatest Precautions; and at other times by such as withdraw themselves from infected Places into the Neighbourhood.

I own it cannot be demonstrated, that when the Plague makes great Ravage in any Town, the Number of Sick shall never be great enough to load the Air with infectious Effluvia, emitted from them in such Plenty, that they may be conveyed by the Winds into a neighbouring Town or Village without being dispersed so much as to hinder their producing any ill Effects; especially since it is not unusual for the Air to be so far charged with these noxious Atoms, as to leave no Place within the infected Town secure: insomuch that when the Distemper is at its Highth, all shall be indifferently infected, as well those who keep from the Sick, as those who are near them; though at the beginning of a Plague to avoid all Communication with the Diseased, is an effectual Defence. However, I do not think this is often the Case: just as the Smoak, with which the Air of the City of London is constantly impregnated, especially in Winter, is not carried many Miles distant; though the Quantity of it is vastly greater than the Quantity of infectious Effluvia, that the most mortal Plague could generate.

But, to conclude what relates to the Air, since the ill Qualities of it in these Northern Countries are not alone sufficient to excite the Plague, without imported Contagion, this shews the Error of a common Opinion, countenanc’d by Authors of great Name[60], that we are necessarily visited with the Plague once in thirty or forty Years: which is a mere Fancy, without Foundation either in Reason or Experience; and therefore People ought to be delivered from such vain Fears. Since the Pestilence is never originally bred with us, but always brought accidentally from abroad, its coming can have no relation to any certain Period of Time. And although our three or four last Plagues have fallen out nearly at such Intervals, yet that is much too short a Compass of Years to be a Foundation for a general Rule. Accordingly we see that almost fourscore Years have passed over without any Calamity of this kind.

The Air of our Climate is so far from being ever the Original of the true Plague, that most probably it never produces those milder infectious Distempers, the Small-Pox and Measles. For these Diseases were not heard of in Europe before the Moors had entered Spain: and (as I have observed in the Preface) they were afterwards propagated and spread through all Nations, chiefly by means of the Wars with the Saracens.