A woman arrived in Abuja on an international flight from Uganda on October 3. Four days later she developed symptoms. On October 11 she went to a private health facility in the Nigerian capital. On October 20, a laboratory finally confirmed what she had: Ebola caused by the Bundibugyo virus, according to the World Health Organization's regional office for Africa. Nine days passed between the moment she sought care and the moment anyone knew.

The fifth country

Nigeria is the fifth country to detect the Bundibugyo strain since Congo declared its outbreak in mid-May, WHO said. France reported a travel-linked case earlier in the year, Uganda recorded cases before declaring its own outbreak over, and Kenya confirmed an imported case on October 6, as we reported in our account of Kenya's first Ebola case.

The patient is isolated and receiving care. The Nigerian health ministry said the investigation is still working to establish the likely source of her infection and to reconstruct her travel and exposure history. Forty-four contacts had been identified at confirmation and 53 were under follow-up by October 25, the European Centre for Disease Prevention and Control (ECDC) reported. On October 26, she was medically evacuated to Switzerland, according to Nigeria's Coordinating Minister of Health, as cited by the ECDC.

Why nine days

The public record does not say exactly why confirmation took until October 20. It does show a pattern. When Congo's outbreak began, initial samples reportedly tested negative because the tests used could detect only the Zaire species of Ebola, not Bundibugyo. Science reported in May that widely used field tests built for Zaire often miss Bundibugyo. In Kenya, the first patient was initially treated as a viral fever before samples were sent, per the health minister's briefing.

None of this is carelessness. It is what happens when a virus arrives in places that have prepared for a different version of it. A private clinic in Abuja facing a feverish traveller from Uganda has no obvious reason to order a test for a rare species. The practical lesson is that a negative result from a Zaire-focused assay does not clear a patient who has a plausible exposure, and that the delay between first care and first test is where an outbreak gets its head start.

Kenya's cluster

Kenya's numbers have also moved. As of October 26, nine confirmed cases, including two deaths, have been reported in Kenya, all linked to the first imported case, ECDC said. The second death, on October 23, was the third confirmed case in the cluster.

The pattern of those eight secondary cases is the notable part. As of October 23, they were four relatives and four health care workers, all already in quarantine when they developed symptoms, the ECDC reported. That is the best-case version of a hospital cluster. The workers were infected before anyone suspected Ebola, which is how the first patient was treated, but they were caught as contacts, not as unnoticed carriers. Kenya was following all 135 listed contacts as of October 22, and the US Centers for Disease Control and Prevention says the Kenyan health ministry has reported no community spread.

The source is still burning

Both cases trace back to the outbreak in Congo, which keeps growing. As of October 25, Congo had reported 10,060 confirmed cases and 4,887 deaths, according to the CDC and ECDC. In the latest reporting period, 96 new cases and 46 new deaths were added, mostly in North Kivu (58 cases) and Ituri (32), the ECDC said.

WHO's own count, as of October 20, was 9,704 cases and 4,687 deaths across 66 health zones in eight provinces, a crude case fatality ratio of 48.3 percent. Contact tracing stood at 76.9 percent as of mid-October, according to Congo's health ministry, as reported by ABC News. UN News notes that there is currently no vaccine for this virus, so control still depends on finding cases quickly, isolating them and tracing contacts.

What the exported cases say

Each country that has reported a case shares one feature: the traveller passed through Uganda or came from Congo, and the diagnosis was made after arrival. That is a clue about where the earliest warning has to happen. Screening at one border cannot catch a person who is not yet symptomatic, and it is only as good as the test behind it.

It also explains the choice WHO made to urge all countries in the region to sustain a high level of readiness. The agency stressed that rapid identification of cases, timely follow-up of contacts and effective infection control are critical to preventing further spread.

What to watch

Ebola can take up to 21 days to show symptoms after exposure, so Nigeria's contact follow-up will run well into November. The second marker is whether any Nigerian contact falls ill. The third is Kenya: whether its cluster stays at nine and whether the health workers who were infected recover.

The most informative number in this outbreak may not be a case count. It is the number of days between a person's first visit to a clinic and a positive test. In Nigeria it was nine, and for an incubation period measured in days, that is a long time.

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