The World Health Organization (WHO) was not told that Nigeria's Ebola patient had travelled to Congo, the WHO's representative in Nigeria said on Thursday, after Uganda said she had visited the country.

Nigerian health authorities have said the country's first Ebola case in more than a decade involved a Ugandan woman who had recently arrived from a trip there.

Uganda's health ministry said the woman had travelled to Congo, where the outbreak was first declared in mid-May and has since grown into the fastest-spreading on record.

Pavel Ursu, the WHO representative, told an online press conference: "The information supplied to WHO did not include travel to another country (other than Uganda)."

"The facts which we have received is that the patient returned to Abuja on October 3 being away from September 16 in Uganda," he added.

Ursu said the focus in Nigeria was now on containing the viral infection and that the patient remained hospitalised, with her biochemical markers improving.

Jean Kaseya, director of Africa's top public health agency, told Reuters on Wednesday that the patient, the Ugandan-born wife of a Swiss diplomat, arrived in Abuja after a two-week holiday in Uganda.

Patrick Otim, a WHO emergency response manager, said on Thursday the source of her infection was still unknown as health authorities were working to piece together her travel history. 

One issue that is under investigation is which health facilities the woman visited in Abuja after the onset of her symptoms and before her hospitalisation on October 9, Otim continued.