Make the first sentence usable
Lead with the reason for writing so the recipient does not have to decode a long emotional introduction. For a message about how to tell contacts you may have exposed them to illness, use this factual base: separate symptoms, diagnoses, medication, dates, and clinician advice from assumptions or internet research.
Reduce the work of responding
Offer simple options, a narrow question, or a clear update that can be understood without another conversation. Ask for the record, appointment, review, accommodation, or care decision through the correct channel. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Respect the boundary already visible
Do not share another person's medical information or treat a message as a substitute for clinical advice. Contact local emergency or urgent medical services for severe, worsening, or immediately dangerous symptoms. A block, explicit refusal, legal restriction, or safety plan takes priority over the desire to explain more.