Source of Nigeria's First Ebola Case in Over a Decade Remains Unclear as Fears of Wider Spread Grow

Health authorities across Africa are trying to establish how Nigeria's first Ebola patient in more than a decade became infected, amid worries that the outbreak could spread further now that it has reached a fourth African country.

The Swiss foreign ministry said on Friday that the patient is the Ugandan-born wife of a Swiss diplomat based in Abuja. According to the ministry, she had not travelled to the Democratic Republic of Congo, where the outbreak was first detected in mid-May before moving on to Uganda, Kenya and now Nigeria. The ministry said she was believed to have caught the virus while travelling with her husband in Uganda.

That account conflicts with earlier statements from Uganda, which had said the woman travelled to eastern DR Congo. It also raises questions about whether authorities can contain an outbreak that is already the most geographically widespread on record. Uganda reported Ebola cases in May and June, and the World Health Organization declared the country Ebola-free in August. A Ugandan government spokesperson told Reuters on Thursday that Uganda had no Ebola cases and would make the information public if it did.

The WHO said investigations into the likely source of the Nigerian infection are continuing. Catherine Smallwood, a WHO Ebola incident manager in DR Congo, told a UN briefing in Geneva via video link that WHO staff in DR Congo had no information indicating the patient had travelled to that country.

The Africa Centres for Disease Control and Prevention is looking into whether the patient may have come into contact with an Ebola patient in Kenya. Both travelled through Uganda's Entebbe airport on 3 October, according to Dr Wessam Mankoula, the organisation's head of emergency preparedness and response. Smallwood said a link to the Kenyan case was possible, but officials would need to compare the timing with the onset of the Nigerian patient's symptoms to judge whether infection was more likely at the airport or elsewhere.

Some experts are doubtful. Marion Koopmans, a Dutch virologist and member of the WHO's Ebola emergency committee, called the theory "very speculative unless there is evidence of sharing the same space in a manner that could explain that." She added that random presence at a large airport is "not a supported epidemiological link by any standard of what we currently know."

Nigeria's health minister, Muhammad Ali Pate, said the case remains contained and contact-tracing is continuing. "We are trying to contain it so it doesn't go out to the communities," he said.

Melaku Yirga, vice-president for Africa at Prosper Global, formerly Mercy Corps, said confirmed cases in Kenya and Nigeria show that countries must work closely together. He stressed speed, cross-border information sharing without delay, and giving frontline health workers and local organisations the resources to respond quickly.

The outbreak is caused by the rare Bundibugyo virus, for which there is no approved treatment or vaccine. First announced on 15 May, it has infected more than 9,500 people and killed nearly half of them. It is the largest and deadliest outbreak in DR Congo's history and the second largest globally, behind the 2014-16 west Africa epidemic, which infected more than 28,600 people and killed more than 11,000.