Is there a form somewhere that my partner can sign saying they are aware of a persons status?
aware of your status or somebody else's? Either way, it doesn't matter, there are no forms to fill out. If you want to have something official, you will need to have something in writing yourself, with both of your signatures. If you want to make it official letter take it to a lawyer or have it notarized. Otherwise just an instant messenger chat being printed out showing that HIV status was disclosed is good enough.
Ive never heard of one