This newspaper is from Kenya, March 15, 2018:
Differences on North Korea key to Trump's Tillerson decision.
The following excerpt is interesting - does not quote sickness but desire to come back to USA before announcement of him being let go:
Tillerson, who was in Nairobi at the time and still had two stops to go - Chad and Nigeria - asked that he first return to the United States before it was announced.
The next thing for the State Department after this trip appears to be a meeting in Vienna regarding the Iran Deal:
It was not immediately clear whether Tillerson’s policy chief, Brian Hook, would stay on beyond March 31. The department announced on Wednesday that Hook would travel to Vienna to participate in a meeting on Friday on the Iran nuclear deal.
https:// www.standardmedia.co.ke/article/2001273300/differences-on-north-korea-key-to-trump-s-tillerson-decision-sources