Jasper has tested positive for FeLV. It would be best for Jasper to be the only cat OR share a home w/other FeLV+ cats.
How is FeLV spread? http://www.vet.cornell.edu/fhc/brochures/felv.html
Cats persistently infected with FeLV serve as sources of infection. Virus is shed in very high quantities in saliva and nasal secretions, but also in urine, feces, and milk from infected cats. Cat-to-cat transfer of virus may occur from a bite wound, during mutual grooming, and (though rarely) through the shared use of litter boxes and feeding dishes. Transmission can also take place from an infected mother cat to her kittens, either before they are born or while they are nursing. FeLV doesn't survive long outside a cat's body—probably less than a few hours under normal household conditions.