A 50-year-old woman who tested positive for Ebola in Uganda has died, a health ministry official told AFP Thursday, the second fatality since the virus spread from neighboring Democratic Republic of the Congo.

"The deceased has been confirmed as the grandmother of the 5-year-old boy who died. Both victims had attended the burial of an Ebola patient in Congo, but returned to Uganda," the official told AFP on condition of anonymity.

Arrangements are being made to bury the woman in Kasese, a district in western Uganda close to the DRC ­border, the official added.

The health ministry announced Wednesday that Uganda had recorded three cases of Ebola infection in the first known cross-border spread since an outbreak began in eastern DRC in August.

All three were from a single family that traveled to DRC to care for a relative, who also died of Ebola.

The 5-year-old later died and his 3-year-old brother and 50-year-old grandmother tested positive for the virus upon returning to Uganda.

The family was quarantined in a hospital in Bwera, in Kasese district. Eight others who had been in contact with them were also being monitored in an isolation ward.

East Africa has been on high alert since the outbreak was declared in the eastern DRC provinces of North Kivu and Ituri. 

More than 2,000 cases have been recorded in DRC - around two-thirds of them fatal.