THE NOSOI (or Nosi) were the spirits (daimones) of illness, plague and disease. Hesiod describes the nosoi escaping from Pandora's jar, and like Elpis (Hope), they were probably personified to a certain degree. However, in most Homeric literature it is the arrows of the gods Apollon and Artemis which bring plague, rather than a band of daimones. The Roman equivalents of the Nosoi were Morbus, Lues, Pestis, Tabes and Macies. The Greek Keres also occasionally personified killing disease.

THE NOSOI SPIRITS OF PESTILENCE & DISEASE

Hesiod, Works and Days 90 ff (trans. Evelyn-White) (Greek epic C8th or C7th B.C.) :
"For ere this [the opening of Pandora's jar] the tribes of men lived on earth remote and free from ills (kakoi) and hard toil (ponoi) and heavy sickness (nosoi) which bring the Keres (Fates) upon men; for in misery men grow old quickly. But the woman took off the great lid of the jar (pithos) with her hands and scattered all these and her thought caused sorrow and mischief to men. Only Elpis (Hope) remained there in an unbreakable home within under the rim of the great jar, and did not fly out at the door; for ere that, the lid of the jar stopped her, by the will of Aigis-holding Zeus who gathers the clouds. But the rest, countless plagues (lugra), wander amongst men; for earth is full of evils and the sea is full. Of themselves diseases (nosoi) come upon men continually by day and by night, bringing mischief to mortals silently; for wise Zeus took away speech from them. So is there no way to escape the will of Zeus."

Aeschylus, Agamemnon 1001 ff (trans. Weir Smyth) (Greek tragedy C5th B.C.) :
"Truly blooming health (hygeia) does not rest content within its due bounds; for disease (nosos) ever presses close against it, its neighbor with a common wall.  So human fortune, when holding onward in straight course strikes upon a hidden reef. [N.B. Hygeia and Nosos are scarcely personified in this passage.]"

MORBI SPIRITS OF PESTILENCE & DISEASE (LATIN)

In Latin poetry various aspects of pestilence and disease were personified, including Morbus (Disease), Pestis and Lues (Pestilence), Macies (Wasting, Emaciation), and Tabes (Corruption). They are presumably equivalent to the Greek Nosoi.

Virgil, Georgics 3. 551 ff (trans. Fairclough) (Roman bucolic C1st B.C.) :
"On this land from the sickened sky there once came a piteous season that glowed with autumn's full heat [a great dearth followed by hunger and disease] . . . Ghastly Tisiphone [an Erinys] rages, and, let forth into light from Stygian gloom, drives before her Morbus [Nosos, disease] and Metus [Phobos, dread], while day by day, uprising, she rears still higher her greedy head."

Seneca, Oedipus 582 ff (trans. Miller) (Roman tragedy C1st A.D.) :
"[The seer Teiresias performs necromancy to learn the cause of the pestilence ravaging Thebes :] Suddenly the earth yawned and opened wide with gulf immeasurable. Myself, I saw the numb pools amidst the shadows; myself, the wan gods and night in very truth. My frozen blood stood still and clogged my veins. Forth leaped a savage cohort [of ghosts] . . . Then grim Erinys (Vengeance) shrieked, and blind Furor [Lyssa, fury] and Horror [Phrike, horror], and all the forms which spawn and lurk midst the eternal shades [i.e. in the underworld]: Luctus [Penthos, grief], tearing her hair; Morbus [Nosos, disease], scarce holding up her wearied head; Senectus [Geras, age], burdened with herself; impending Metus [Phobos, fear], and greedy Pestis [Ker or Nosos, pestilence], the Ogygian people’s curse. Our spirits died within us. Even she [Manto] who knew the rites and the arts of her aged sire stood amazed. But he, undaunted and bold from his lost sight, summons the bloodless throng of cruel Dis [Haides]."

Seneca, Oedipus 647 ff :
“[The ghost of Laius demands Oidipous be expelled from Thebes before he will recall the pestilent daimones ravaging the land to Haides :] `Wherefore speedily expel ye the king from out your borders, in exile drive him to any place so-ever with his baleful step. Let him leave the land; then, blooming with flowers of spring, shall it renew its verdure, the life-giving air shall give pure breath again, and their beauty shall come back to the woods; Letum [Ker, ruin] and Lues [Ker or Nosos, pestilence], Mors [Thanatos, death], Labor [Ponos, hardship], Tabes [Phthisis, corruption] and Dolor [Algos, distress], fit company for him, shall all depart together. And he himself with hastening steps shall long to flee our kingdom, but I will set wearisome delays before his feet and hold him back. He shall creep, uncertain of his way, with the staff of age groping out his gloomy way. Rob ye him of the earth; his father will take from him the sky.'"

Seneca, Oedipus 1052 ff :
"[After Oidipous has blinded himself and sets out in exile he calls for the daimones of pestilence to depart from Thebes :] `All ye who are weary in body and burdened with disease, whose hearts are faint within you, see, I fly, I leave you; lift your heads. Milder skies come when I am gone. He who, though near to death, still keeps some feeble life, may freely now draw deep, life-giving draughts of air. Go, bear ye aid to those given up to death; all pestilential humours of the land I take with me. Ye blasting Fatae [Keres, fates], thou quaking terror of Morbus [Nosos, disease], Macies [Ischnasia, wasting], and black Pestis [Ker or Nosos, pestilence], and mad Dolor [Algos, despair], come ye with me, with me. ‘Tis sweet to have such guides.'"

Sources:

• Hesiod, Works & Days - Greek Epic C8th-7th B.C.
• Aeschylus, Agamemnon - Greek Tragedy C5th B.C.
• Virgil, Georgics - Latin Idyllic C1st B.C.
• Seneca, Oedipus - Latin Tragedy C1st A.D.