[the phantom]

Let's stop the wild theories and rebuttals for a moment and examine this thing logically. If you do, I believe you will come to the same conclusion that I did about this.

Maedhros literally killed Lalaith. Not indirectly, but with his own flesh.

Follow me through some points here-
1) Morgoth's plague was a specific response to the growing power of Maedhros.
2) Morgoth was seriously evil. If some sort of evil plan occurs to me, it's a given it occurred to him.
3) The plague was not conjured from nothing. Melkor could not create life or matter. He could only take existing things and corrupt them.
4) The plague had to have some sort of source- i.e. a biological "patient zero". Some animal or bit of flesh had to be Morgoth's test tube, which he then placed somewhere in the north and the sickness spread from it.

Given those facts, does any diabolical idea spring to mind?

No?

Well, perhaps you're not as sick and twisted as I am by nature, so I'll make this easy for you. Given that it was the power of Maedhros that Melkor was striking against, wouldn't it be absolutely perfect to use Maedhros as the engine of destruction?

"But Phantom- Morgoth couldn't get to Maedhros, and Tolkien never said he was sick!"

Ah, but you're forgetting that not every bit of Maedhros was accounted for. What about the hand he left behind hanging upon the cliffs of Morgoth's fortress!!

Given the facts, you can't tell me that Morgoth didn't have this idea. The hand was infected and Morgoth had his servants plant it near some populated area around Hithlum and boom- horrible death brought about by Maedhros's own flesh! He brought doom upon Lalaith, literally with his own hand.