What causes a cat to lose it's voice?

she was very vocal,..I really am worried about her. she acts the same, she has a big appetite, drinks water normally, and she's so cute and affectionate..but when she meows I can barely hear her voice now she seems to cough a little bit sometimes, a week ago she was in heat. I kept her indoors. she is scheduled to be spayed. I didn't have time to take her to the vet because I worked over time. If she contracted something would she spread it to my other cats? my other cats are all vaccinated against everything. this kitten is from a cat that had kittens that my sister found and I happened to look after so I kept one of her kittens( my cat) I took the mother cat to the vet and was negative for FIV, the vet said mother cat was healthy. What could cause a cat to lose it's voice?

A cat can strain their vocal cords just like humans. They can also get laryngitis.

SInce you have her scheduled for a spay...make sure she is not ill before the operation. They should be completely healthy before undergoing surgery. By the way, somethimes when my dog would bark a lot, she would get a little horse. I often wondered if cats get sore throats and headaches just like we do.