Bill Gates, the richest man in the world and philanthropist, pledged to invest an extra $5 billion in helping youth in Africa particularly those affected by health epidemics like malaria, AIDS, Ebola and Zika virus.

The Microsoft co-founder was delivering the Nelson Mandela Annual Lecture in Johannesburg, South Africa, on Sunday a day before Mandela Day. He is also in the country to attend an AIDS conference that will start on Monday.

Every year, the Nelson Mandela Foundation organizes a lecture series, which offers prominent leaders a platform to address thorny social issues. other leaders that have previously talked at the lecture include former US president Bill Clinton, former UN Secretary-General Kofi Annan and Michelle Bachelet, the first female president of Chile.

Gates said the Bill & Melinda Gates Foundation has already invested over $9 billion in Africa in the last 15 years, mostly in health related projects, according to Economic Times.

He said Africa’s youth should be given a chance to grow and get a better education as this was fundamental to the continent’s overall development.

“The youth must be given an opportunity to thrive. We must clear away the obstacles that keep young people from growing,” he said, adding that Africa has the world’s youngest demographics.

“By 2050, 40 percent of the world’s children will live on this continent,” Gates said.

Despite perennial political instability, widespread diseases and other issues affecting Africa, the billionaire philanthropist thinks that there is hope in the continent’s youth and said they are key in determining the direction for the future.

Gates drew his personal example of starting Microsoft at the age of 19 that helped him grow his wealth to over $77 billion, and other American tech entrepreneurs like Steve Jobs and Mark Zuckerberg who started young, as what African youth can achieve if given an opportunities, Forbes reported.

“The African entrepreneurs driving startup booms in the Silicon Savannahs from Johannesburg and Cape Town to Lagos and Nairobi are just as young—in chronological age, but also in outlook,” Gates said.