All of the fatalities have been adult men, and a total of 91 people had contracted the disease as of Dec. 8.
Symptoms include headache, fever and vomiting blood, but Ebola and bubonic plague have so far been ruled out as the cause.
Ugandan health workers say they have developed a treatment that has so far halted the death toll at 38.
Northern Uganda, where the outbreak is currently confined, is still recovering from 20 years of civil war.
Poverty and poor sanitary conditions make the region vulnerable to contagious diseases.