The Nigerian president’s chief of staff has tested positive for the coronavirus, a source with direct knowledge and several diplomats said.
The illness of Abba Kyari, who is in his seventies, brings the disease into the immediate circle of President Muhammadu Buhari, 77.
Mr Kyari has a history of illness including diabetes, and is the gatekeeper to the president.
Many who wish to deal with Mr Buhari must go through Mr Kyari, even Nigeria’s top politicians and executives.
He travelled to Germany in early March with a delegation of other Nigerian officials for meetings with Siemens AG. It is unclear whether he self-isolated upon his return home.
A presidency spokesman did not comment on whether Mr Buhari has been tested for the virus. The president himself has undisclosed ailments, and spent five months in London for medical treatment in 2017.
Matthew Page, an associate fellow with the Africa Programme at Chatham House, described him Kyari as the "lynchpin" of the Buhari government.
"This has the potential to further slow down decision making within top tiers of Nigerian government," he said.
As of Monday, Nigeria had 40 confirmed cases, two of whom had recovered, and one death - a 67-year-old former oil official. It was unclear if Kyari's diagnosis was included in that total.