Doctors across Northern Ireland have been sent letters to distribute to more than 40,000 patients considered to be at "at risk of severe illness" if they contract coronavirus.
The letters advise the patients to stay at home and avoid all face to face contact for at least 12 weeks, except for carers and healthcare workers.
A template letter has been sent by the Northern Ireland Health and Social Care Board to all GPs. Doctors are being asked to forward the letters to patients they believe are particularly vulnerable and at risk.
The letter opens with a stark warning: "We have identified that you, or the person you care for, is at risk of severe illness if you catch Coronavirus (also known as Covid-19)".