A second case of Ebola has been confirmed in Liberia just months after the country had been declared free of the disease, according to health officials.

The five-year-old son of a 30-year-old woman who died on Thursday has now been taken to a treatment centre in Monrovia, Tolbert Nyenswah, the country's deputy health minister, said on Sunday.



"We are investigating in both Guinea and Liberia how she entered," he said. "But knowing the porous border we are not surprised. She entered Liberia before getting sick or manifesting signs and symptoms."



Authorities are now checking everyone the woman was in contact with and 10 health care workers from the hospital where the woman was treated are also under observation.

The woman, who died on arrival at the hospital on Thursday, had travelled with three of her children.



Setback for Liberia



The new cases are a setback for Liberia, which had been declared free from transmissions for a third time on January 14.



The country was first declared free of the disease in May, but new cases have emerged twice, forcing officials to reset the clock in a nation where more than 4,800 people have died.

The World Health Organization (WHO) has said Ebola is no longer an international health emergency, but flare-ups, at a decreasing frequency, are expected.

Flare-ups have also broken out in Sierra Leone and in Guinea.

Guinea to vaccinate contacts of Ebola survivors

The WHO said there have been eight cases of Ebola and seven deaths in Guinea since late February. There now are no known cases in Sierra Leone.

Ebola is spread through direct contact with the bodily fluids of victims or corpses. It has killed more than 11,300 people, mostly in West Africa, since December 2013.