SAHARSA (AFP) - Hundreds of thousands of flood victims huddled into makeshift camps in India and Nepal face major disease outbreaks if help fails to reach them quickly, aid workers warned Tuesday. They said several camps in India's northern Bihar state and across the border in Nepal, areas devastated when a monsoon-swollen river burst its banks and changed course, were already reporting cases of diarrhoea and other crippling illnesses. A large part of Bihar is under water, with 550,000 people displaced and a further 400,000 people still awaiting rescue, state officials said. According to the UN's World Health Organisation, three million people have been affected in some way. At least 60,000 people have also had their homes washed away in southern Nepal, officials there said. "After two to four days, because of the stagnant water, more people will get sick. There will be more illnesses," government health worker Jai Krishna Sah told AFP at a crowded relief camp in Saharsa district, 150km east of Bihar's state capital Patna. In many areas, wells have been inundated with floodwaters carrying silt, sewage, bodies and refuse. "The important thing now is for there to be some camp management, where the people have access to latrines, clean drinking water and some basic health care," said European Commission humanitarian aid representative Malini Morzaria. One flood survivor, Sunita Yadav, was carrying a bucket of muddy water that she said she was going to use to make porridge. "I am using this water to cook with or drink. What are we to do?" she said. The relief operation in Bihar is proving slow going - and dangerous. Most people reaching safety are traumatised by the loss of their homes, crops or loved ones, and carry few or no possessions. At least 15 people drowned overnight Monday in two separate accidents involving overcrowded rescue boats taking stranded villagers to safety, Bihar state disaster official Pratyay Amrit told AFP. The dead included many children who were washed away by the strong currents still gushing through Supaul and Madhepura districts, two of the worst-hit areas. At least 100 people have been confirmed dead since the Kosi river overwhelmed decrepit flood defences in Nepal and shifted course two weeks ago. Lieutenant-General H S Panag, the Indian army official coordinating relief work, said the floods were "the biggest national calamity in recent times." A government statement said more army units, aircraft, boats and divers as well as tents and other emergency supplies were being sent to the area. It said 25,000 people were now being rescued each day. Bihar state's chief minister, Nitish Kumar, also suggested the humanitarian crisis was likely to be extremely serious for several weeks. The northern and northeastern states of Uttar Pradesh, West Bengal and Assam have also been badly hit by monsoon floods. Impoverished Nepal is meanwhile struggling to help 60,000 homeless people on its side of the border. "People have started suffering from fever, pneumonia and diarrhoea," said Sanjeev Kafle of the Nepal Red Cross. "We fear there is a high chance of outbreaks of diseases like cholera and Japanese encephalitis."