Rescued a cat and found out that it has feline leukemia. It’s a virus.

The female cat that I already had before I brought in this new cat was vaccinated 5 months ago for feline leukemia among other things and has not had a lot of contact with my new rescued cat due to the fact that I needed to take new cat vet first as a precaution. They saw each-other through a kennel and my cat slapped at the new cats head like a total butthole and that was it. But I am still absolutely freaking out because feline leukemia is very very bad. I need someone to ease my mind here because I am very very attached to my girl cat. In my head I know my cat was vaccinated and is more than likely completely fine but my anxiety is like “bitch wtf now your cat is sick.”