if my opponent was stupid enough to special summon a monster with 1500 attack or less while Deck Devastation Virus's effect was still continuing, wouldn't that monster be destroyed?

Stupid nothing. He gets the monster. You check their field and hand on activation, and their draws for three turns, but if they pull one out some other way, it's all theirs.

nice. thanks..........50 cccccccchhhhhhhaaaaaarrrrrraaacccttteeerrrrssss!!!

Deck Devastation Virus only affects the field during its initial resolution (when it checks the field and the hand for 1500 or less monsters).

Afterwards, it ONLY looks at the cards that are "drawn" for the effect.

Anything added to their hand, "picked up", Special Summoned from the Deck/Graveyard/Removed from play Area and such will NOT be affected by Deck Devastation Virus after it checks everything.

It does not continuously check the field and the hand for the next 3 turns, just the cards the opponent "draws".