It's a little reported disaster, largely hidden from cameras by the ravages of internecine warfare.
Almost 800,000 people in Yemen have been affected in the world's deadliest outbreak of cholera, and the World Health Organisation expects that number to climb to one million by the end of the year.
Thousands of people have died from the acute diarrhoeal infection caused by ingestion of contaminated food or water.
Almost half of the victims have been children, according to the UN Office of the Co-Ordination of Humanitarian Affairs.
Now the UN is warning that Bangladesh's plans to build the world's biggest refugee camp for 700,000 Rohingya Muslim refugees could heighten the risks of diseases such as cholera spreading quickly in that country.
"When you concentrate too many people into a very small area, particularly the people who are very vulnerable to diseases, it is dangerous," Robert Watkins, the UN resident coordinator in Bangladesh, told Agence France Press, adding Bangladesh should look for sites to build new camps.
"If there are infectious diseases that spread, that will spread very quickly," he said.
Bangladesh, trying to cope with a potentially catastrophic emergency at its border with Myanmar, has asked the International Organisation for Migration (IOM) to co-ordinate the work of other agencies to build a mega-refugee camp on 1200 hectares of land, alongside a huge existing camp.
The new camp will dwarf the world's largest existing camps in Uganda and Kenya, both which house around 300,000 refugees.
More than half a million Rohingya have fled a brutal offensive by Myanmar's security forces in Rakhine since late August in the largest movement of a civilian population in Asia since the 1970s.
More than 300,000 Rohingya who had fled earlier violence were already living in squalid refugee camps across the border in Bangladesh, unable to return to Rakhine where Buddhist-majority Myanmar refuses to grant Rohingya citizenship and other basic rights, despite the fact that they have lived there for generations.
And according to the IOM as many as 100,000 more Rohingya may be waiting to cross the border to escape what the UN has described as a campaign of ethnic cleansing and what human rights groups say amount to crimes against humanity.
Bangladesh, one of the world's poorest and overcrowded nations, insists the Rohingya will only allowed to remain in the country temporarily.
But Hayton, Associate Fellow, Asia Program at Chatham House, said policymakers must not hide behind the faction that Bangladesh is only temporarily hosting the refugee population in preparation for a rapid return home.
"Over-optimist assumptions now will lead to worse misery in the long term," he said."Instead, the world needs to plan on the basis that Bangladesh will be hosting a very large permanent refugee population."
Meanwhile, Reuters reports that United States and European Union are considering targeted sanctions against Myanmar's military leaders over the Rakhine atrocities.
Until now much of the criticism for the disaster has been levelled at Myanmar's de factor leader Aung San Suu Kyi who has failed to speak up for persecuted Rohingya.
But Reuters quotes diplomats saying the military and specifically top generals should be targeted in any punitive action.
Washington was moving to consult other nations, Reuters said.
The Turnbull government has resisted calls for Australia to cut ties with Myanmar's generals who ruled the country with an iron-fist before allowing a semblance of democracy in 2011.
Myanmar's government has denied its security forces are conducting a campaign of ethnic cleansing and claimed they launched only cleansing operations after attacks by Muslim insurgents.
