Misty is a FIV carrier. The FIV virus weakens the immune system so they need monitoring for infections and dental issues, but if they are well cared for they can live long and normal lives. FIV cannot be spread to humans, dogs or other animals. FIV+ cats can live with FIV- cats if there is no risk of fighting and if cats are spay and neutered. It is advised to separate any new introductions until you are sure they will not fight to minimize risks.
See more at Best Friends Animal Society's homepage: https://bestfriends.org/resources/fiv-cats-faqs-feline-immunodeficiency-virus