Edit: Just because we CAN bring someone back, doesn't make it a good idea. That goes for the past as well as the now. If it really is such a 'serious threat', why don't we just send a big ol' C17 with a load of Hazmat gear, set up a base IN AFRICA with the qualified personnel and use that as an aid/ research station. The cynic in me says this obviously hasn't been thought of.
That makes a lot of sense, though the risk is still there with aircraft coming back and forward to the UK.