Genomic sequencing has linked Ebola cases detected in Kenya and Nigeria to the same transmission chain and to viruses circulating in eastern Democratic Republic of Congo, while leaving open the possibility of an undetected chain in Uganda.

Scientists from the four affected countries jointly reviewed 1,126 viral genomes after the Nigerian case was detected in the capital Abuja, according to Jean-Jacques Muyembe, the veteran Congolese virologist who convened the analysis.

The genomes from Kenya, Nigeria and Beni in eastern Congo form a single genetic group, Muyembe said Wednesday. The Beni virus carries the same genetic “barcode” found in the Kenyan and Nigerian samples, including a mutation not seen in other sequenced viruses from Congo.

The Nigerian patient visited Uganda from Sept. 15 to Oct. 3 — a period that entirely overlapped with her possible exposure window — before returning to Abuja and developing symptoms three days later. The Kenyan index patient traveled from Congo through Uganda from Oct. 1 to Oct. 3 before flying from Entebbe to Nairobi, while the Nigerian patient also flew from Entebbe that day.

Neither carry genetic markers associated with Uganda’s known Ebola transmission chains from May and June, meaning the cases weren’t descended from those documented outbreaks.

Still, sequencing cannot establish where the two patients were infected or by whom. Scientists can’t yet determine whether the Nigerian patient was infected through the Kenyan transmission chain, or whether both cases originated from a separate, previously unidentified source, Muyembe said at an ministerial meeting on Ebola.

The countries are now reconstructing the patients’ movements to determine whether their itineraries overlapped and to identify fellow travelers if they did. Uganda was asked to intensify surveillance among travelers and in border districts for evidence of an unrecognized chain.