Population: 22.1 million (2005)
Population: 131.5 million (2005)
HIV/AIDS: Six percent of the population had AIDS or was infected by HIV in 2003, which equals almost 4 million Nigerians and more than 8 percent of the global total.
HOW TO HELP
These organizations all devote considerable time and money to solving the problems that impact the African continent. Visit each Web site to learn how you can help.
Bono TV: Into Africa
May 21: The U2 front man talks about the opportunities and problems facing Africa, and looks forward to his trip across the continent with "NBC Nightly News" anchor Brian Williams.
Population: 9 million (2005)
HIV/AIDS: 5 percent of the population has HIV/AIDS, filling 80 percent of available hospital beds.
Population: 13.5 million (2005)