I never knew. One evening, we left the house to go shopping briefly. When we came home and I was putting groceries away, she started screaming and went into convulsions. We grabbed her (I have a memory of Penny licking the top of her head, like she was saying, "what's the matter, baby?") and jumped into the car and sped to an Emergency Vet office. She died 5 minutes after we got there. The stupid vet then, even though we'd asked him to, never did any tests to find out what it was or if it was even communicable to the other cats, because "she died, what's the point?" I nearly killed him.

But that was about 2 weeks before I moved out of my ex-husband's house so I wasn't exactly in the most stable of emotional health anyway.