Are there any diseases, besides rabbies and cat scratch fever?

That can be transfered from cats to humans.
My sister has five beautifull cats, all were strays and now they are well cared for and loved. She also feeds a two strays that come around.One of them is pretty sick and mangy but too wild to catch and help, she has been bitten by this one.. I know one of her cats is AIV. My sister has been very sick with continuous emptying of the bowel for two months. No food stays in her body for more than an hour. Tests have been done, for human conditions and nothing has been found. I was curious if anyone has any idea if she has been infected by one of her cats. Help!!

Edit: FIV
She has had the stool sample done, I mentioned that, they found nothing in the stool

She needs to have stool samples analyzed to she what she has if she has not had this done. Also, she needs to go to a gastroenterologist (one that specializes in bowel problems). He/she may be able to help. Without a diagnosis, it is impossible to tell if this is related to her cats.

Parasite from cats can be transfered to humans

yes some times the parasites from the cats can be transferred from the cats , when they are infected ,to the humans and they suffers with , if you want to try homoeo medicine for this then:
YOU GIVE 1ST HYDROPHOBINUM 1M ONE DOSE OVER CLEAN TONGUE IN EMPTY STOMACH, THEN YOU GIVE
ARSENICUM ALBUM 200 AND BELLADONNA 200, TAKE 5 ML EACH AND INSTILL 2 DROPS EACH TIME FOUR TIMES A DAY FOR A WEEK AND SEE THE MAGIC,IF WANT MORE CAN E-MAIL ME.

It could be something that the cat is a carrier of but it doesn't effect the cat! It could be in their litter box, or an allergy to cats.

I doubt it, but toxoplasmosis is why pregnant women can't empty a litter box - could kill the baby. There's plenty of diseases that transfer, and even more that transfer via parasites and bugs on the cats. Too many for us here without a professional - so do that instead.