Nigerian President Muhammadu Buhari’s publicity chief has refused to disclose any more details on Buhari’s health, fueling fears after the ailing leader made the latest in a series of trips to London for specialist treatment.

Femi Adesina, Buhari’s special adviser on media and publicity, said “it’s only Mr. President that can say what exactly is wrong with him.”

Speaking to the Nigerian Tribune, Adesina cited the Hippocratic Oath and doctor-patient confidentiality as the reasons for the secrecy. “It is within his prerogative to do that [update people on his health status]. Nobody can do it for him. Not even the doctors treating him can do it for him. Under the Hippocratic Oath, nobody can do it except [for] the patient,” he said.

Buhari left Nigeria for London in January to consult with specialists, and returned in March. Last Sunday, he repeated his trip to London for further treatment.

Nigerians have been awaiting news about their president, who has been suffering health problems for a number of years, and the lack of official updates has frustrated many. There are rumors that Buhari may in fact be dead.

In his absence, Africa's most populous nation is gripped by its worst economic crisis in decades, and is facing the double threat of famine and the Boko Haram insurgency. This is not a good time for a power vacuum or any kind of uncertainty.

Adesina noted that it was Buhari himself who provided details about his health after an earlier trip to London to treat an ear problem.

“When he came back, he told the country that this [ear issue] was what was wrong with him. So, the prerogative is his own to disclose and if he wants to disclose, he will. But nobody should be asking him to do it. That would be an infringement on his rights.”

However, many are worried that Buhari may be sicker than officials admit. Silence, it appears, is only adding to this suspicion.