Kitten cough

I was rereading the first warriors book, Into the Wild and during Firepaw's first gathering Runningnose says that a disease called kitten cough kills kits because twolegs destroyed a grove of a herb that cures it. I have read many books and none of them ever say anything more about kitten cough so, maybe all the kits that just mysteriously die, die from kitten cough? If so, why hasn't any medicine cat noticed? [it might have happened in the newest books but, I haven't read them yet]