A 5-year-old Congolese boy who traveled with his family into Uganda has died from the Ebola virus, international health officials said on Wednesday — a day after the case was confirmed as the first appearance of the highly contagious disease outside the Democratic Republic of Congo since an outbreak began there a year ago.

The case, first reported by the World Health Organization on Tuesday, was identified soon after the child entered Ugandan territory. Nonetheless, it represented a new threat that the outbreak in Congo had crossed into a neighboring country.

By Wednesday, the World Health Organization said in a tweet that two more cases of the virus had been identified in Uganda; both patients are relatives of the boy who died.

The outbreak in Congo, the second largest on record, has infected more than 2,000 people and caused 1,390 deaths since it was discovered in July 2018. The number of cases has accelerated in recent weeks, health officials said.