Anadolu Agency via Getty Images In the central and south parts of Somalia, extreme drought makes people vulnerable to diseases such as cholera and diarrhea. There are very limited water sources in the region.

GENEVA, April 13 (Reuters) - More than 25,000 people in famine-threatened Somalia have been struck by cholera or acute watery diarrhea and the deadly epidemic should double by this summer, the World Health Organisation (WHO) said on Friday.

The United Nations is already racing to avoid a repeat of famine in the drought-hit Horn of African nation where more than 250,000 people died of starvation in 2011.

Cholera, which is endemic in Somalia, is an acute diarrhoeal disease that can kill within hours if left untreated. Malnourished children under five years are especially vulnerable.

Already 25,424 infected people have been identified since the start of the year, WHO spokesman Tarik Jasarevic said by email, adding: “These numbers are projected to increase to 50,000 by summer.”

The case fatality rate for the disease, spread by contaminated food or water, is already 2.1 percent in Somalia, twice the emergency threshold, he said. At least 524 deaths have been recorded.

Cholera can be successfully treated with oral rehydration solution. Severe cases will need rapid treatment with intravenous fluids and antibiotics, according to the WHO.

Death rates among Somalis infected with cholera now reach 14.1 percent in Middle Juba and 5.1 percent in Bakool, U.N. spokesman Jens Laerke told a news briefing.

“We still have 2.9 million people in level 3 and 4, level 4 being the step just before we declare a famine,” Laerke said, referring to the U.N. classification. “So almost 3 million in those critical and crisis emergency levels.”

The center of cholera outbreak is Baidoa, David Akopyan, U.N. Development Programme (UNDP) deputy country director for Somalia, told the briefing by telephone from the capital Mogadishu.

Thirteen of Somalia’s 18 regions are affected, he said.

Some 500,000 Somalis have been internally displaced, many in search of water, as well as some 3 million pastoralists who have lost 70 percent of their livestock due to drought, he said.

Akopyan, asked about famine, replied: “We are not exactly there, the fear is that in two months if things are not scaled up we will get there ... Hopefully famine will be prevented.”