An outbreak of hepatitis E has infected at least 1050 Sudanese refugees in South Sudan, killing 26 and threatening to spread further among people still arriving in crowded camps, the United Nations has confirmed.

About 175,000 people have already fled to South Sudan to escape fighting in Sudan's South Kordofan and Blue Nile states, according to the UN High Commissioner for Refugees, and thousands more are expected to cross in coming weeks after the rainy season ends.

Hepatitis E is mainly transmitted via contaminated drinking water.