I'm referring to things that exist already. Sex is generally private, but if somebody is transmitting STDs while they do it, they are subject to public health contact tracing, which goes like this: https://www.ncsddc.org/wp-content/uploads/2017/08/infographi...

Actual details vary by state, but this is how CA does it: https://dhs.saccounty.net/PUB/Pages/Communicable-Disease-Con...

This seems reasonable to me. I don't think the right to privacy extends as far as the right to secretly give people diseases, especially ones that cause permanent damage and possible death.