KAMPALA, Uganda — The death toll for Uganda's mysterious disease has risen to 38 people.

The Uganda Health Ministry announced that preliminary results from tests done at the Central Public Health Laboratories (CPHL), Uganda Virus Research Institute (UVRI), USAID, CDC Atlanta and WHO on specimens obtained from patients are negative for Ebola, Marburg, Congo Crimean Fever, Rift Valley and Typhoid. Further tests are being run to identify the cause of the illness.

As of December 3, 2010, there were 91 patients and 38 deaths.Thirteen people have died in northeastern Uganda from the unknown disease.

Investigations are continuing to determine the cause of the disease that appears to be similar to the Ebola and Marburg hemorrhagic viruses.

Ninety-one cases of the frightening illness have been reported in the remote Abim district. Due to the number of cases reported, the district has been labeled the epicenter of what many are calling it the “Abim disease.”

Of the 20 cases in Abim, eight have died, two are quarantined and another 10 have been discharged after their conditions improved, according to . Five more died in the neighboring Agago district.

“The victims usually die between three and five days, and are suspected to be highly contagious,” said Emmanuel Okech, a health official in Abim.

Symptoms include high fever, vomiting blood, passing bloody stool, convulsions and bleeding from openings like the nose and ears.

“We do not know what we are dealing with, we do not know what is happening, so we must respect the new measures which have been put in place,” said Dr. Emmanuel Otto, a health officer in Agago district, which has also been affected by the disease.

Health officials warn against communal hand washing, eating bush meat (meat from wild animals, especially monkeys and other primates) and discourage people from the local cultural practice of washing dead bodies before burial.

District health officials set up an isolation center for thos with the disease in Abim Hospital and another local health center.

“People have been advised against shaking hands, to maintain personal hygiene and basically to stay away from groups of people and avoid burials,” said Martin Koriang, a businessman from the Abim area.

Representatives from the World Health Organization joined Dr. Otto and his team in Abim and Agago. They visited the sick and took blood samples to investigate the disease.

The symptoms of the disease are similar to the Ebola and Marburg viruses, diseases that also cause a deadly hemorrhagic fever.

“Blood samples have been taken to the Uganda Virus Research Institute in Entebbe. The people of this area await the results, so we can know how to deal with this,” said Dr. Otto.

Blood samples from affected persons have also been flown to the Centers for Disease Control in Atlanta, Georgia.

The new disease bears several similarities to Ebola hemorrhagic fever, which has a reputation for mutating and changing. Ebola is a severe and often deadly illness that can occur in humans and in primates like monkeys and gorillas.

Ebola hemorrhagic fever has made worldwide news because of its destructive potential. Ebola fever is caused by a virus belonging to the family called Filoviridae.

Scientists have identified four types of the Ebola virus. Three have been reported to cause disease in humans: Ebola-Zaire virus, Ebola-Sudan virus, and Ebola-Ivory Coast virus. The human disease has so far been limited to parts of Africa.

A very small number of people in the United States who were infected with the fourth type of the virus, known as Ebola Reston, did not develop any signs of disease.

The disease can be passed to humans from infected animals and animal materials. Ebola can also be spread between humans by close contact with infected bodily fluids or through infected needles in the hospital.

There is no known cure for Ebola. Existing medicines that fight viruses (antivirals) do not work well against the Ebola virus.

The patient is usually hospitalized and will most likely need intensive care. Supportive measures for shock include medications and fluids given through a vein. Bleeding problems may require transfusions of platelets or fresh blood.

As many as 90 percent of patients die from the disease. Patients usually die from shock rather than blood loss. Survivors may have unusual problems, such as hair loss and sensory changes.