An outbreak of hepatitis E has infected at least 1,050 Sudanese refugees in South Sudan, killing 26 and threatening to spread further among people still arriving in crowded camps, the United Nations said on Friday.

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

"To date, 26 refugees have died in camps in Upper Nile (state)," UNHCR spokesman Adrian Edwards told a news briefing in Geneva.

"The capacity to contain an outbreak of hepatitis E among the refugee population is increasingly jeopardized. The risks will grow if, as currently anticipated, we see fresh inflows of refugees from South Kordofan and Blue Nile states," he said.

The death toll was up from 16 on September 13.

The virus, contracted and spread through contaminated food and water, damages the liver and can be fatal.

To counter spread of the disease, the UNHCR was struggling to provide 15 to 20 liters of safe drinking water per refugee per day and building enough latrines so that each unit is shared by no more than 20 refugees, said Edwards.

The agency needs at least $20 million by the end of the year for its South Sudan operation as only 40 percent of its appeal for $186 million has been received, he added.