@ehBeth,
The employee has to report a couple of illnesses herself/himself to employer - all those which might be dangerous to others.
Physicians have to report to the local health department a couple of illnesses, either anonymously (like e.g. AIDS, HIV, plasmodium/malaria) or with the name of the patient (nearly all dangerous infections). (There are slight difference from state to state.)
The Federal law (in German)
>here< (§6 - §15) (
not official English version (pdf-data, and not the latest version of the law)
The local health department reports it to the state ministry ... (There are special regulations/by laws for this as well)