Feline immunodeficiency virus (FIV) causes an infectious disease in domestic cats similar to human immunodeficiency virus in humans. It attacks and weakens the body’s immune system, making the animal susceptible to infections and diseases that don’t affect healthy cats. There is neither a cure nor a vaccine for FIV. FIV is transmitted primarily through deep, penetrating bite wounds. A mother cat may transmit the virus to her newborn kittens during gestation, passage through the birth canal, or nursing.