GENEVA, Oct 19 (Reuters) - The World Health Organisation (WHO) said on Friday it was investigating a suspected outbreak of yellow fever in Sudan, which has killed nearly 30 people.

The viral disease, which causes jaundice in some patients, is transmitted by mosquitoes but can be confused with malaria, typhoid, viral haemorrhagic fevers and hepatitis.

"We have 31 suspect cases including 28 deaths. Samples are being tested, we should know early next week whether it is yellow fever or not," said WHO spokesman Gregory Hartl.

The outbreak was near the Nile about three hours from Khartoum and the samples were being sent to a laboratory in Cairo for analysis, he said.

Yellow fever symptoms include fever, muscle pain, nausea and vomiting, but most patients improve after three to four days, according to the United Nations health agency.

Some 15 percent of patients enter a "toxic phase" within 24 hours, with bleeding from the mouth, nose, eyes or stomach as kidney function deteriorates. Half die within two weeks.

There is no specific treatment for the disease, which has caused large epidemics in Africa and the Americas, except for oral rehydration salts and paracetamol.

Intensive care may save the most seriously ill patients, but it is rarely available in the poorest countries. Vaccination is important for rapid control of outbreaks, according to the WHO.

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