I can totally understand your concerns and fears!

But moosmom has posted some very good infos on FeLV here , and this should be interesting for you:

Will I infect my healthy cat if I pet an FeLV+ cat, then pet my cat?

No. Not unless you were to go immediately from one cat to another, and have wet saliva, urine or blood on your hand. Even then the chances would be slim. FeLV needs to be transferred through the media above, and will not live long outside the host (the infected cat). Warm, dry environments will deactivate the virus and common household detergents and disinfectants will eliminate it from any contacted surfaces. If you wash your hands with soap after touching an infected cat, you will not infect an FeLV negative cat.

As far as I know, the same goes for FIv as well.

Kirsten