Acting president Goodluck Jonathan officially became Nigeria's new leader Thursday following the death of Umaru Yar'Adua from a long-term illness on Tuesday night. Yar'Adua was 58.

Jonathan, who was the African nation's vice president, had been serving as its leader since February, three months after Yar'Adua left for Saudi Arabia to be treated for an inflammation of the lining around the heart. It is not clear if Jonathan will run for president in 2011.

In the time Yar'Adua was in office, he helped broker a cease-fire in 2008 with rebels in the oil-rich Niger River Delta. Since then, the main rebel group, the Movement for the Emancipation of the Niger Delta, said it was resuming hostilities. Nigeria also is struggling with the effects of a financial crisis in 2008 and 2009 due in part to plummeting oil prices.

Although polio has been wiped out in most of the world, it is a growing problem in Nigeria. NewsHour special correspondent Fred de Sam Lazaro reports on efforts to fight the disease.

A swath of northern, predominantly Muslim states in Nigeria adopted hard-line Islamic law, sparking clashes among residents and posing problems for the government.

Following Nigeria's independence from Britain in 1960, the country's political life has been marked by cycles of corruption, instability and military coups. Read about Nigeria's leaders here.