The week is over, so I guess we're done with the Silent Letters theme.

Pity. I was waiting for the word to be PSITTICOSIS, also known as Parrot Fever.

Then we could have the letter changed be Greek PSI, and make

PSI --> MU: MUTTICOSIS = Mixed-Breed-Dog Fever, or
PSI --> OMEGA: OMEGATTICOSIS = "I can't even imagine such a terrible plague," or...

Opportunity squandered. Rats.