You should consult with a local plaintiff employment attorney to be sure, but there is no such thing as employer/employee confidentiality or privilege. Barring such a privilege (ie., attorney-client, priest-penitent, doctor/therapist-patient) people are under no legal obligation to keep your secrets. Furthermore, here, they had to take action so others would not become infected. Also, HIPAA applies to medical facilities, not employers.
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In some instances you have a privacy right violation you can bring if certain information is disclosed. However, here it appears that you disclosed your condition which you were not legally obligated to do in order to be excused from work. Also, if the shingles affected your vision I assume it was on your face and if you returned to work just two days later the shingles would have still been obvious. More information would be needed to give more specific response. I recommend you speak with local counsel.