The UN warned of a humanitarian "nightmare" unfolding in Bangladesh's refugee camps, where half a million people have taken shelter after fleeing violence in Myanmar in unprecedented waves.
With a lack of clean water and toilets, aid workers said a major health disaster is imminent.
Heavy monsoon rain is compounding the risk of disease outbreak, with field doctors reporting a huge spike in cases of severe diarrhea, especially among children.
The near daily torrential downpours send streams rushing through areas where tens of thousands openly defecate every day. For some, this murky runoff is their only source of drinking water.
A stench of excreta hangs in the air on the outskirts of Kutupalong, a camp that already housed tens of thousands of refugees before the latest influx saw it mushroom into a fetid tent city stretching for miles.
At a field clinic, a long queue of refugees waiting to see the only doctor available stretched beyond the tent into the pouring rain.
Dr. Alamul Haque sees upwards of 400 patients a day and looked exhausted as he described the spiraling number of children presenting with water-borne illnesses.
"Earlier parents were bringing one or two children with them. Now it's three to four," Dr. Haque, from Bangladeshi charity SDI, told AFP.
"It's been raining, so human waste is running everywhere. There is a high chance of a diarrhea epidemic here."
Meanwhile, new groundwater wells are being dug quickly across the camps, which stretch along the Cox's Bazar district bordering Myanmar.
But there remains a serious shortage of fresh water, with the sheer scale of the disaster -- described as one of the fastest-growing refugee crises in years -- outpacing aid efforts on the ground.
Source: News Agencies, Edited by website team