Uganda is "burning the midnight oil" with international health experts to give a name to an unknown illness which has claimed the lives of 38 people in the north of the country.
The unknown illness was first detected on November 10 in several districts in the central part of northern Uganda, according to a statement from the health ministry.
Local and foreign media reports had identified the illness as bubonic plague, which has previously struck Uganda, most recently in 2008.
But an official from the ministry's Epidemiology and Surveillance Division working closely on the outbreak said Wednesday that the disease remained mysterious and evidence collected so far pointed away from bubonic plague.
"The results we have received from Fort Collins are negative for bubonic plague," the official, who requested anonymity, told AFP, referring to a specialized laboratory in the US state of Colorado.
"If this was typical plague, we would have found that out by now. We just haven't seen a disease like this before," he added.
The doctor explained that all previous incidents of plague in Uganda were contained in the West Nile region, much further west than the current outbreak.
The source added that plague victims suffer from inflammation in specific body parts, including the armpits, which has not happened in this case.
"The plague we've seen in the past also tends to cause fatalities among women and children, but all the dead here are adult men," the official also said.
The doctor said that while Uganda-based staff from the US Centers for Disease Control (CDC) were already working on the case, specialists from CDC headquarters in Atlanta were on their way to help identify the illness.
Staff from the World's Health Organization's Africa regional office in Brazzaville, Republic of Congo have also been sent to Uganda.
"We simply don't have the information to conclude what this disease is yet, but we are working around the clock, literally 24 hours," the official said.
Ugandan staff have developed a treatment that has so far halted the death toll at 38, according to the source.
The 91 confirmed patients reported severe headaches, dizziness, fever, diarrhoea and vomiting, according to the health ministry.