Ebola still has the “upper hand” in the outbreak that has killed more than 1,400 people in West Africa, but experts have the means to stop it, an American expert has said.

Two new cases of Ebola have emerged in Nigeria and are outside the group of medics who treated a man who arrived in the country sick and later died, Health Minister Onyebuchi Chukwu said.

Liberian security forces have sealed off a seaside slum in the capital Monrovia in the latest effort to stop the spread of Ebola, setting off protests by angry residents.

Liberia is facing an excruciating choice – deciding which handful of Ebola patients will receive an experimental drug that could prove either life-saving or life-threatening.

The doctor who treated a man who flew to Nigeria and died of Ebola has now contracted the disease, authorities said.