Dadaab , Kenya ( CNN ) -- Humphry Musyoka , a doctor at the world 's largest refugee camp , knows well how quickly dehydration can ravage the body of a child . A young girl who seems OK one minute can turn on a dime . But Musyoka , who works at the Dadaab refugee complex in Kenya , says he has no time to think about loss . `` More are still coming , so we have to do something about that , '' he told CNN 's Anderson Cooper . `` It 's very challenging mentally , I 'd say , because you lose life . But what do you do about the next one ? '' `` How are you going to respond ? '' he asks . Such are the questions aid agencies are struggling to answer as fighting and famine push hundreds of thousands of Somalis to Dadaab , located near the border . The United Nations has declared famine in five areas in southern Somalia , including the capital of Mogadishu . The human catastrophe was triggered by the worst drought in more than half a century and compounded by decades of conflict , high inflation and increasing global food and fuel prices . In all , about 12 million people in the Horn of Africa region need assistance ; Somalia is the worst hit . Originally built for less than 100,000 people , the Dadaab refugee complex now houses more than 400,000 , while tens of thousands more cling to its edges . Many of the children who arrive at the camp are severely malnourished , according to relief workers . Some have spent weeks on the road with their mothers , walking at night to avoid the heat , braving dust and dirt storms . Extra beds have been added to the children 's ward of a hospital , run by the International Rescue Committee . A six-month old , suffering from diarrhea and vomiting , weighs six pounds . He should be twice that . A listless , four-year-old girl is fed what looks to be fortified milk from a plastic mug ; a hand props up her head . Still , they are the lucky ones , says CNN 's Sanjay Gupta . About 29,000 children have died in the last month , according to U.N. estimates . And many who are sick will never recover . One such girl was Sarah . Her father , Aden Ibrahim , buried her body beneath the desert floor some two weeks ago . She was four . `` She needed more help , '' Ibrahim said then . `` We have not been given enough help because we have been given flour and maize only -- and a child who is sick will not get better on flour and maize . '' The U.N. 's refugee agency is calling for more private and government donations for emergency operations in the Horn of Africa , warning that a lack of funds threatens future aid . The aid organization says it needs $ 145 million to cover operations through the end of the year , adding that it has received 45 % of that amount so far . CNN correspondent David McKenzie recently revisited Ibrahim , who is now confined to his bed inside a makeshift tent . `` I have n't been able to do anything since I saw you last , '' said Ibrahim , weakened by fever and coughing fits . `` All I can do is lie in bed with my son . ''
Fighting and famine push Somalis to Kenya 's Dadaab complex . Many of the children who reach the camp are severely malnourished . They are the lucky ones , says CNN 's Sanjay Gupta . The U.N. estimates 29,000 children have died in the last month .