Dear Friend,
A most answerable question and need a good approach. First, take the employee in confident, rather than get rid of the employee better give an opportunity to live a normal life by the employee giving him the works that can be managed by him/her. Convey the nearest medical cell about the employee and to the medical board, the prime thing you have to do. Provide him leave as and when required to get medical aids without much delay from your office/work place. Always, provide a place for that employee in case if you cannot provide these facilities, better provide with financial assistance for his living as a measure of welfare to the employees and take care of the situation, this will help stop spreading of the disease, our kindness is the best protector of the society.
Never investigate how he/she got the disease, it is not our agenda, yet, spread how to protect from the disease dreaded to life to others for their benefits...It is very much essential for the good of the organisation...