What happens if Muhammadu Buhari doesn't return to Nigeria?

Nigerians are becoming increasingly concerned with the health of their head of state, Muhammadu Buhari, who has been on medical leave in the UK for more than a month.

In spite of the presidency's efforts to dismiss allegations the 74-year-old leader is severely ill or even dead, fears that Buhari might no longer be able to lead the country are increasing.

Buhari's stay in the UK is shrouded in mystery. Since he left Nigeria on 20 January, the president has not made any public appearance and has spoken only through aides.

The fact that top officials – including the president of the senate Bukola Saraki – have travelled to London to visit the head of state is further fanning suspicions that the leadership is concealing his true condition.

Nigerians, who have been calling on Buhari to personally dismiss allegations of ill health, fear a power vacuum at a time when the country is marred by economic recession, terrorism, famine, widespread corruption and religious and ethnic tensions.

They recall the events of 2009, when former president Umaru Yar'Adua was admitted to a hospital in Saudi Arabia and Nigerians were left to wonder about the future as officials revealed very little information about his deteriorating health.

When he died, Nigeria experienced a power vacuum that was filled only when the senate changed the law to allow the then vice president Goodluck Jonathan to be sworn in. He was later elected president and served until 2015, when Buhari took power.

"The uncertainty about Buhari's health condition could set the stage for power struggle at a time when Nigeria needs calmness in the face of general insecurity made worse by severe malnutrition and famine in the north," David Otto, security analyst and counter-terrorism expert at UK-based TGS Intelligence Consultants, told IBTimes UK.

"If Buhari had been receiving treatment back in Nigeria all this fuss may not have surfaced as it is now. This puts the country at risk of confusion and internal power struggle," he continued.

Could there be a power vacuum in Nigeria?

Buhari appointed Vice-President Yemi Osinbajo as acting president before he left, meaning that if the president should die or become incapacitated, he is already carrying out the role. Equally, if Buhari remains in the UK, there could be a vote to replace him.

"Buhari may be removed as president on grounds of incapacity if two-thirds of his own cabinet resolve that he is no longer physically fit to be president, " said Adedayo Ademuwagun, a Lagos-based analyst at Songhai Advisory.

"Buhari could eventually come back from holiday to reclaim his position as president, but his apparent health problems would likely diminish his capacity to function and also diminish his authority. "

Would Osinbajo become president?

If Buhari dies or become incapacitated, Osinbajo could become the interim president until the country holds presidential elections, which are scheduled to take place in 2019.

Some believe Osinbajo could be good for Nigeria. Since starting his role as acting president, he has already visited the restive Niger Delta region, something Buhari is yet to do. Osinbajo also addressed grievances of protesters who called for economic reforms and launched a 60-day action plan to improve the business climate.

"Having Osinbajo as acting president might be the best Nigeria could hope for at this juncture," Matthew T. Page, analyst and the US government's former top expert on Nigeria, told IBTimes UK.

"I don't think Nigeria will be leaderless, insofar as Buhari was already a very weak leader and others around him have essentially been charting the direction of the country by – as a government official I spoke to on my last trip said – 'reading Buhari's body language'."

But some – including Page – have pointed out that Osinbajo, a Christian from the south, could be obstructed by politicians loyal to Buhari, a Muslim from the north.

"Osinbajo's presidency would likely be met with stiff opposition from northern politicians and Buhari's allies," Ademuwagun explained.

"It is improbable that Buhari's cabinet would expeditiously trigger his removal even if he is truly incapacitated or has passed away. Northern ministers would likely not support it and they are more than a third of the cabinet," he continued.

It is not clear when Buhari is due to return to Nigeria and speculations about his health are likely to continue unless he makes a public statement. Meanwhile, Osinbajo's star is rising, with many already wondering whether the 59-year-old is preparing to take the lead of Africa's most populous nation.

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