An outbreak of Ebola virus in southern Sudan has infected at least 15 people, killing four of them. A further 100 people are under surveillance, and aid agencies are racing to contain the disease's spread.
Early Ebola diagnosis is difficult as its initial symptoms are similar to those of malaria. But Ebola victims go on to develop internal bleeding, and are likely to die without medical attention.
The World Health Organisation has traced the outbreak to the town of Yambio near the Kenyan border. It is hoped that swift action may avert the deadly outcomes of recent outbreaks in Uganda and Congo, during which hundreds died.