An analysis said that the disease originated in Africa less than 6,000 years ago, and that it was carried across the Atlantic by seals.

Soldiers and the police blocked roads to a neighborhood of tens of thousands of people in Monrovia, Liberia’s capital, and residents hurled rocks and stormed barricades trying to break out.

The 10-year-old boy, found without his family, was eventually transported to a hospital in Monrovia.