We've been looking into the possibility its the brand of food we give them, since we and my aunt feed the same food to our cats (and my older brother lives with my aunt, so his cat gets that food, too) however, we're pretty sure its some sort of bug. Even so, we're giving them some different foods and see if that does anything. We feed our cats canned Wellness. Also, all the cats had blood work done, but it all came back normal.
My brother's cat, who is usually so skittish you can hardly touch him without him putting his ears back and hissing at you, was so sick you could pet him, pick him up, basically do anything to him. He didn't even care when we gave him fluids and medicine.
My aunt has even canceled most of her vet appointments with cats for fear of bringing the bug to her client's cats.
Ohh, my cat Bramble loves his belly rubbed! Jigsaw, too, though not as much. My female cats, however, will shy away if you try to rub their bellies.
Hehe, Amarni is playing with a cap to a syringe right now. She's picking it up in her mouth, tossing it into the air, and batting it halfway across the room. So adorable <33 XD