Lucretius, De Rerum Natura
William Ellery Leonard, Ed.

Now, of diseases what the law, and whence
The Influence of bane upgathering can
Upon the race of man and herds of cattle
Kindle a devastation fraught with death,
I will unfold. And, first, I've taught above
That seeds there be of many things to us
Life-giving, and that, contrariwise, there must
Fly many round bringing disease and death.
When these have, haply, chanced to collect
And to derange the atmosphere of earth,
The air becometh baneful. And, lo, all
That Influence of bane, that pestilence,
Or from Beyond down through our atmosphere,
Like clouds and mists, descends, or else collects
From earth herself and rises, when, a-soak
And beat by rains unseasonable and suns,
Our earth hath then contracted stench and rot.
Seest thou not, also, that whoso arrive
In region far from fatherland and home
Are by the strangeness of the clime and waters
Distempered?- since conditions vary much.
For in what else may we suppose the clime
Among the Britons to differ from Aegypt's own
(Where totters awry the axis of the world),
Or in what else to differ Pontic clime
From Gades' and from climes adown the south,
On to black generations of strong men
With sun-baked skins? Even as we thus do see
Four climes diverse under the four main-winds
And under the four main-regions of the sky,
So, too, are seen the colour and face of men
Vastly to disagree, and fixed diseases
To seize the generations, kind by kind:
There is the elephant-disease which down
In midmost Aegypt, hard by streams of Nile,
Engendered is- and never otherwhere.
In Attica the feet are oft attacked,
And in Achaean lands the eyes. And so
The divers spots to divers parts and limbs
Are noxious; 'tis a variable air
That causes this. Thus when an atmosphere,
Alien by chance to us, begins to heave,
And noxious airs begin to crawl along,
They creep and wind like unto mist and cloud,
Slowly, and everything upon their way
They disarrange and force to change its state.
It happens, too, that when they've come at last
Into this atmosphere of ours, they taint
And make it like themselves and alien.
Therefore, asudden this devastation strange,
This pestilence, upon the waters falls,
Or settles on the very crops of grain
Or other meat of men and feed of flocks.
Or it remains a subtle force, suspense
In the atmosphere itself; and when therefrom
We draw our inhalations of mixed air,
Into our body equally its bane
Also we must suck in. In manner like,
Oft comes the pestilence upon the kine,
And sickness, too, upon the sluggish sheep.
Nor aught it matters whether journey we
To regions adverse to ourselves and change
The atmospheric cloak, or whether nature
Herself import a tainted atmosphere
To us or something strange to our own use
Which can attack us soon as ever it come.