Abba Kyari, one of the closest advisers to Nigerian President Muhammadu Buhari, died Friday after contracting the novel coronavirus, becoming the highest-profile casualty of the virus in Africa’s biggest economy.

Buhari named Kyari, a former chief executive officer of United Bank for Africa Plc, as his chief of staff in August 2015, and renewed his appointment after winning a second term in office. Behind the scenes, he was regarded as one of the powerful politicians in the country of more than 200 million people.

Kyari tested positive for the virus after returning from a trip to Germany, the presidency said in a statement.