The primary mode of transmission is through bite wounds.
Casual, non-aggressive contact among cats does not appear to be an efficient route of spreading FIV.  Sexual contact probably is not a primary means of spreading FIV.

I just discovered that one of my cats is infected with FIV, yet I have other cats as well.  What do I do now?

Cat-to-cat transmission of FIV in multiple-cat households where there is no fighting among cats appears to be quite uncommon.

Can I become infected with FIV from an infected cat?

No, most certainly not.  Although FIV is structurally similar to HIV (the human immunodeficiency virus) and causes a disease in cats similar to AIDS in humans, it is a highly species-specific agent and affects only felines.

How long can I expect my FIV-positive cat to live?

It is impossible to accurately predict the life expectancy of a cat infected with FIV.  Under ideal conditions, such as isolation of the FIV-infected cat from other cats, many cats will remain in apparent good health for many months to a number of years after the initial infection.

My FIV-positive cat died recently after a long illness.  Is it safe to bring a new cat into my home?

Feline immunodeficiency virus is fairly unstable outside the cat and will not survive for more than a few hours in most environments.  In addition, transmission of FIV occurs primarily through bites, so a waiting period between cats is not required to prevent FIV infection.