The Ebola patient in Nigeria is a Swiss woman, and the wife of a staff member at Switzerland's embassy in Abuja, Bern said Friday.
The couple had recently travelled together to Uganda, but neither of them had visited the Democratic Republic of Congo -- the epicentre of the current outbreak, the Swiss foreign ministry said.
On Tuesday, Nigeria announced its first recorded Ebola case, saying it was a woman who arrived in Abuja on a flight from Uganda. A total of 44 contacts have been identified.
On Wednesday, the authorities confirmed that the patient had the Bundibugyo species of Ebola, which is driving the outbreak in the DRC and for which there are currently no specific vaccines or treatments.
Switzerland's foreign ministry said Friday she was "the wife of a Swiss member of staff" at Bern's embassy in the Nigerian capital Abuja.
"The Swiss woman, who is symptomatic, has been hospitalised for about a week at a private clinic in Abuja," it said in a statement.
"The infection may have occurred during a trip to Uganda approximately two weeks ago," the Swiss authorities added.
"Her husband is in isolation; he has shown no symptoms. He accompanied his wife on the trip, during which she is believed to have contracted the Ebola virus," it said.
"Neither individual travelled" to the DRC, it added.
The ministry said that the 25 other embassy staff members -- eight Swiss nationals and 17 local employees -- "are also doing well".
Following consultations with the Nigerian health ministry and the World Health Organization (WHO), they do not need to go into isolation, the statement said.
Bern is considering the "potential repatriation of the patient" to Switzerland, it added.
The WHO said the patient developed symptoms on October 7, four days after arriving in Nigeria; sought care in Abuja on October 11; before testing positive for Bundibugyo on October 20.
"National authorities, with support from WHO and partners, have intensified contact tracing, case investigation and infection prevention and control measures, including the provision of essential supplies and personal protective equipment for health workers," the UN health agency said in an update.
"Investigations are ongoing to establish the likely source of infection and reconstruct the travel and exposure history.
"WHO advises against any restriction of travel to, or trade with, affected countries," it added.
Following the DRC, Uganda and Kenya, Nigeria has become the fourth African country to be affected by the Bundibugyo outbreak, which flared up in northeastern DRC in May.