paulwork

erm... last time I checked there was no AIDS virus.   There is, however, an HIV virus.   And you can't pass it on via sex if you are HIV positive and are on treatment.   PS Germany recently liberalised access to PREP meds, so things are starting to go in the right direction for HIV prevention.   https://www.aidshilfe.de/meldung/prep-will-soon-available-50-euros-germany-starting-seven-cities

It's not the best approach, but in the face of homelessness, if as far as the landlord is concerned, you never moved out, you could just say there was a mistake at the amt, they automatically deregistered you when a letter went stray and didn't arrive, and now you have to correct it with a re-register.   Amts deregister people automatically all the time (even though they shouldn't) when mail doesn't get delivered / lost in post / name tag falls off bell / whatever.   The landlord could decide to dig further though. But let's face it, Amts right now are impossible to get hold of due to staff shortages / Amt staff temporarily being re-assigned to Ukraine welcome centers / civil servants retiring and nobody wanting to replace them. So good luck to the tenacious landlord who has the patience to spend hours sending emails / making phone calls to Frau / Herr whoever who no longer works there, or only between the hours of 07:00 and 08:00 once a month in a leap year.   HOWEVER... If you have a good relationship with the landlord, and a good fingertip feeling that they wouldn't hold it against you (not likely with a faceless Liegenschaftverwaltung) then ignore all of above and come clean.