Feline leukemia is a viral disease that affects cats, caused by the feline leukemia virus (FeLV). This virus can weaken a cat's immune system, making them more susceptible to infections and other diseases. It is primarily spread through saliva, urine, and feces, often through close contact with infected cats. Cats infected with feline leukemia may show symptoms such as weight loss, lethargy, and fever. Some cats can live for years without showing signs, while others may develop serious health issues. Regular veterinary check-ups and testing can help manage the risks associated with feline leukemia.