Plague Chess

In Plague Chess, each side starts out with an extra piece, the "diseased" (or leper, carrier, etc.). The disease piece carries an infectious illness that their own side is resistant to (resistance in a population) but the other side is susceptible to. Enemy pieces that are adjacent to the diseased piece for at least one turn pick up the disease as well. Diseased enemy pieces can spread the disease to their adjacent teammates as well. The plague's symptoms are like so:

For every turn that a piece has the disease, the amount of possible spaces that they can move decreases. Let's use a rook as an example. In an optimal situation, the maximum amount of spaces that a rook could move would be 7: a rook can jump an entire rank or file on the 8x8 board, not counting their own occupied square. On a rook's second "infected" turn, their longest possible move would be 6 spaces. On the next turn, the rook would only be able to move 5 spaces. This would continue until the rook was crippled and could only move one space. The next turn is fatal and the rook is removed from play.

The same rules apply to bishops and queens.

Infected knights would have to have different symptoms; perhaps they would be weakened every second turn after infection, first losing the ability to jump other pieces and then having the extending section of their "hook" movement grow shorter every two turns.

The king is immune to the disease because of his constant attention from court medical experts (and also because the king's death would defeat the purpose of checkmate). Pawns, being lower-class and exposed to more diseases every day, are immune as well. Optionally, bishops could have the ability to cure or cleanse other pieces, purging them of the disease.

Due to the vast amount of information needed to be remembered in this chess variant, it would be nearly impossible to play in real life, and computer simulations would have to be used.

I apologize in advance if this makes no sense.