A president who’s flown abroad to seek medical treatment and given no firm date for his return: Nigeria has been here before.

Muhammadu Buhari, 74, traveled to the U.K. on Jan. 19 for medical tests and was due back on Feb. 5. He’s yet to return and hasn’t appeared or spoken in public for more than three weeks after asking lawmakers for medical leave.

On Monday, he talked by phone with U.S. President Donald Trump, giving cheer to his supporters that he’s not as ill as widely speculated. Yet his absence is heightening concern about government paralysis at a time when the economy is in recession and the stock market is sliding.

For many Nigerians the situation recalls former President Umaru Musa Yar’Adua’s time in office. Like Buhari, Yar’Adua was a northern Muslim with a southern Christian vice president in a country with often sharp sectarian divisions.

Yar’Adua was flown in November 2009 to Saudi Arabia for treatment of a heart condition. It took about three months for the legislature to appoint then-Vice President Goodluck Jonathan acting president, as Yar’Adua associates sought to cover up the severity of his condition.

Yar’Adua eventually died in office on May 5, 2010. Unlike Yar’Adua, Buhari formally transferred power to his vice president, Yemi Osinbajo, before departing.

“The experience of 2010 still hangs over Nigeria,” Antony Goldman, head of London-based PM Consulting, said by phone from London. “Partly as a result of that the government has undertaken all the efforts to do what wasn’t done in 2010.”

Under the constitution, if Buhari can’t continue in office, Osinbajo would become president and he would choose a new deputy.

Political Jockeying

That’s not stemmed rumors of politicians jockeying for position to succeed Buhari, a former military ruler. The presidency has only said that Buhari is undergoing medical checks and has declined to disclose further information about his condition.

On Monday, Buhari spoke to Trump about the need for more equipment to deal with one of the worst crises the nation is facing -- the fight against the Islamist militant group Boko Haram in the northeast where thousands of people have been killed, more than 2 million have fled their homes and the United Nations is warning of a widespread humanitarian crisis.

Buhari is facing a raft of additional challenges. Even as the central bank holds the naira around 315 per dollar on the official market, it’s tumbled to a record low of 507 on the black market amid a dearth of foreign investment and as shortages of foreign-exchange mount.

Gasoline prices that were to be slashed by two-thirds have risen about 67 percent since he took office. Africa’s second-biggest economy likely had its first full-year contraction in a quarter-century in 2016, while inflation is at an 11-year high.

Stocks Fall

Since his departure, Nigerian stocks have fallen 4.5 percent to a nine-month low. They’ve dropped 6.9 percent this year, the world’s worst performance among 96 primary indexes tracked by Bloomberg.

“The concern may be the effectiveness of government,” said Olusegun Sotola, senior researcher at the Initiative of Public Policy Analysis in Lagos. “Constitutionally, Osinbajo can do almost anything, but it may be another thing in practice.”