Thousands of Rohingya men and women lined up in intense heat at makeshift health centres on Tuesday, many with young children in their arms, to receive the oral vaccine against the disease.
The UN is working with the Bangladesh government to vaccinate 650,000 people living in the sprawling camps against cholera, which spreads through dirty water and can kill if left untreated.
"These people lack most of the basic services -- toilets, water sanitation and everything," UNICEF spokesman A M Sakil Faizullah told AFP.
"When we have this kind of situation, there's a heavy possibility of a cholera outbreak."
Nearly 520,000 Rohingya Muslims have arrived in Bangladesh since late August, fleeing a military crackdown in neighbouring Myanmar that the UN has said likely amounts of ethnic cleansing.
Poor and overpopulated Bangladesh has struggled to cope with the mass influx of people, many of whom have to travel for days or even weeks to reach safety and arrive exhausted and malnourished.
The influx had slowed in recent weeks, but now appears to have picked up again. An estimated 10,000 new refugees arrived on Monday.
World Health Organization workers supported by around a thousand local volunteers plan to vaccinate 650,000 Rohingya over the coming weeks.
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