The Ugandan Ministry of Health says a patient tested positive for Ebola in what is the first transboundary case of the deadly virus since the outbreak began in neighboring Congo last year.
The ministry said today that the patient is a Congolese woman in a district near the Congo border.
Confirmation of cross-border contamination is a blow to local health authorities who monitor the border and isolate the likely patients with ebola.
There have been more than 2,000 confirmed and probable cases of the Ebola virus in Congo since August, with nearly 1,400 deaths.
In April, a WHO expert committee decided that the Congo outbreak, although of "deep concern", was not yet a global health emergency.
The international spread of a disease as contagious as Ebola is one of the main criteria that the WHO considers before declaring that a situation is a global health emergency.
Uganda has had several outbreaks of Ebola since 2000.