Mr Othman replaces Seif Sharif Hamad who died on February 17, 2021.
Tanzania which neighbours the DRC is one of the countries which the WHO has alerted over the Ebola outbreak.
The president declared the country coronavirus free last June, but a spate of deaths led to the concession of Covid-19 existence.
Defence asks the court to examine the legality of his alleged outright kidnap by state agents and rendition to Rwanda.
The East African Business Council executive director had been nominated by President Kenyatta.