France, Oct. 22 -- The Nigerian patient is a woman who returned to the capital, Abuja, from Uganda on 3 October. Kaseya said she had stayed in Kampala, the Ugandan capital, and had never visited the Democratic Republic of Congo (DRC). If his account is correct, it would point to transmission in Uganda, which the Ugandan authorities deny.

Uganda's health ministry said the woman had travelled to eastern DRC on business and only passed through Uganda. On Thursday, Pavel Ursu, the World Health Organization (WHO) representative in Nigeria, said the travel information supplied to the global body mentioned Uganda but no other country.

Kaseya said the woman was not diagnosed until 16 days after arriving in Nigeria, leaving health officials pote...