Disease

Mysterious Haemorrhagic fever outbreak in Sudan

The mystery disease in South Sudan has not been identified but is known to cause fever and unexplained bleeding.

So far, there have been 51 cases — including 10 deaths — from an unknown disease in the northern part of South Sudan. The main symptoms of the disease are similar to those seen with Ebola: unexplained bleeding, fever, fatigue, headache and vomiting.

Scientists have tested 33 of the cases for Ebola, and all of them came back negative. The samples also tested negative for other viruses known to cause unexplained bleeding, such as Marburg virus and Crimean-Congo fever.

Five samples did test positive for O'nyong-nyong -- a mosquito-borne virus closely related to chikungunya. But O'nyong-nyong doesn't cause bleeding and isn't fatal.

"Viral hemorrhagic fever" is a generic term for a group of illnesses caused by four families of viruses. Several of these viruses — such as dengue, yellow fever and Crimean-Congo hemorrhagic fever — are spread by mosquitoes or ticks. When the disease is severe, the virus can damage blood vessels, causing bleeding in organs, under the skin and from the mouth, eyes and ears.

But that's not what kills. The cause of death is typically not loss of blood from bleeding, but from multi-organ failure — especially the kidneys and liver — and shock syndrome from low blood pressure in patients with severe illness.