Deva

• see also 2.09 Croatoan

In 2.09 Croatoan, Sam says, "I've been pawing through Dad's journal, I found something about the Roanoke Colony. Dad always had a theory about 'Croatoan'. He thought it was a demon's name, sometimes known as 'Deva', sometimes 'Resheph', a demon of plague and pestilence."

Considering how the episode ends - with Duane Tanner communicating with an entity much as Meg did in Season 1, saying that "The Winchester boy is immune" (to the virus) - and considering Sam's vision that led them to River Grove, it's reasonable to assume that this 'demon virus' is linked in with The Demon somehow.

Deva

Sam's pronunciation of the name ("Deeva") suggests a relationship to Hinduism wherein a "deva" is used to refer to demi-deities. It is unclear how this usage relates to the daevas seen in 1.16 Shadow.

Monstropedia's discussion of demons in Hinduism traces the etymology of the term 'deva' to suggest its roots in both 'good' and 'evil' deities, and furthermore links the term to 'Asura', relating back to Iranian Zoroastrianism, a religion that crops up frequently in Supernatural's mythology:

Originally, the word Asura ... meant any supernatural spirit—good or bad. Hence even some of the devas (demigods)... have the epithet of Asura. In fact, since the /s/ of the Indic linguistic branch is cognate with the /h/ of the Early Iranian languages, the word Asura, representing a category of celestial beings, became the word Ahura (Mazda), the Supreme God of the monotheistic Zoroastrians. But very soon, among the Indo-Aryans, Asura came to exclusively mean any of a race of anthromorphic but hideous demons.

Indian Myth and Legend by Donald A. Mackenzie further links the etymology to the nature of 'deva':

In the old Persian language, which, like Greek, places "h" before a vowel where "s" is used in Sanskrit, Ahura (= Asura) signifies "god". The Zoroastrian chief god is called Ahura-Mazda, "the wise Lord", as Varuna is addressed in early Rigvedic hymns, "wise Asura and King", and "the all-knowing Asura who established the heavens and fixed the limits of the earth". On the other hand "daeva" in the Iranian dialect, which is cognate with Sanskrit "deva", "god", came to mean "demon". "Asura" is derived from the root "asu", which signifies "the air of life", and "deva" from "div", "to shine", or "deiwo", "heavenly".

-Source

However, 'Deva' can also be considered a spelling variation on Zoroastrian 'Divs' (another spelling is Daeva, the name of the "shadow demons" in 1.16 Shadow).

Wikipedia's entry on Divs suggests that they are more ambiguous than evil, however (or rather, that 'demons' aren't necessarily considered evil in Zoroastrianism, a point Monstropedia makes about Devas in Hinduism also). Wikipedia also translates 'div' directly as 'demon'.

Resheph

According to Wikipedia,

Resheph was a Semitic god of plague and war. He bore the head of a gazelle on his forehead and was an important member of the pantheon of Ugarit though not mentioned in Ugaritic mythological texts.

Christopher Siren identifies Resheph as a Mesopotamian God of pestilence (source).

This is not the first time Mesopotamianism has cropped up in speculation around Supernatural's mytharc; there's a theory that Dean's Amulet is a Mesopotamian figure.