Thousands of people are falling sick as flood waters recede across South Asia, with health workers struggling to cope with inadequate medical stocks.
Air-drops of food and medicine try to ease suffering in Bihar
Ponds of stagnant water are creating breeding grounds for disease.
Thousands have been treated for diarrhoea in India's Uttar Pradesh and Bihar states and a doctor in Bangladesh called his medical centre a "war-zone".
About 28m people have been affected by the floods in India, Bangladesh and Nepal. More than 400 people have died.
Thousands of villages are still under water and although many countries have pledged aid, many areas are desperate for food and clean drinking water.
The Indian government has been given an initial cost estimate of the floods of $320m but the figure is expected to rise.
The rains have halted in most parts of South Asia but with the water receding after two weeks of floods, health workers are now faced with increasing cases of water-borne diseases.
At Bangladesh's biggest diarrhoea hospital in the capital, Dhaka, doctors said they were working round the clock to cope with the rush of flood victims.
"It's like a war-zone situation. Some patients are very ill but the treatment is extremely effective," Dr Alejandro Cravioto told the AFP news agency.
In Uttar Pradesh, LB Prasad, a senior health official told Associated Press that doctors had treated more than 1,500 people for diarrhoea in 22 flood-affected districts in the past 10 days.
However, a private group of doctors in the state says that around 20,000 people there are suffering from water-borne diseases.
"Paramedics visiting affected villages don't have adequate supplies of medicines," Dr Ramadan Ray said.
More than 2,000 villages in the state remain flooded, and an equal number of medical camps have been set up to cope with any outbreak of disease.
THE ASIAN MONSOON
Monsoon winds blow north-easterly for one half of the year, and from the south-west for the other half
South-westerly winds bring the heavy rains from June to Sept
Winds arrive in southern India six weeks before the north west
Annual rainfall varies considerably
In neighbouring Bihar, the government has cancelled leave for doctors in 19 flood-affected districts, state minister Chandramohan Rai told AP.
Unicef has begun inoculation programmes in the state, particularly against measles.
The Indian government has announced initial emergency aid of $37m for flood victims in Bihar.
Heavy rains have also lashed the western state of Gujarat this week, killing at least 15 people and displacing more than 22,000.
Separately, at least 10 people were killed as a huge storm hit Pakistani's largest city, Karachi, on Friday.
They were killed in house collapses and by electrocution.
The UN has blamed the flooding on climate change and says such disasters are becoming increasingly common.
India is the worst-affected country, with some 20 million people in the states of Assam, Bihar and Uttar Pradesh hit by the floods, according to the UN.
Some eight million people are affected in Bangladesh.
About 127,000 people have been displaced in Nepal, with at least 26,500 houses damaged or destroyed, the Nepal Red Cross Society says.