The threat of cholera is like a "ticking bomb" for the hundreds of thousands of Rohingya Muslims who have flooded into Bangladesh in recent weeks, the Red Cross chief warned.
"We have every reason to fear that we can get into a situation that can lead to cholera outbreaks," Elhadj As Sy, head of the International Federation of Red Cross and Red Crescent Societies (IFRC), told AFP in an interview this week.
"We are definitely sitting on a ticking bomb," he warned.
In one of the worst refugee crises in decades, more than 600,000 Rohingya Muslims have crammed into makeshift camps in Bangladesh's Cox's Bazar district since fleeing an army crackdown in Myanmar's Rakhine state, which began August 25.
Poor and overpopulated, Bangladesh has struggled to cope with the mass influx of people, more than half of them children, and many of whom arrive exhausted and malnourished after days and even weeks of travel.
Sy, who spent three days in Cox's Bazar last week, said the conditions there were "difficult to describe" and "very heartbreaking".
One of the biggest concerns is the poor sanitation and lack of hygiene facilities that has sparked growing fears over the emergence of cholera, which spreads through dirty water and can kill if untreated.
The IFRC, which last month opened a field hospital near the camps, has treated numerous patients for acute diarrhoea.
At the same time, the UN began a massive vaccination campaign in a bid to avoid a cholera epidemic, but while no cases have appeared so far, Sy warned unhygenic conditions could see the disease spread.
"Much more must be done so that we don't get into that situation that we are all fearing today."
Cholera is not the only threat. Sy said a surge in measles cases among children in the camps was also "quite worrisome", pointing out that five new cases were detected during a single day of his visit.
So far, 67 cases of the highly contagious virus have been registered, but Bangladeshi authorities insist the situation is under control, with a mass-vaccination campaign underway.
The IFRC field hospital has also treated thousands of people for a range of other ailments, including injuries suffered in Myanmar -- amid widespread accounts of murder, rape and arson -- and along the treacherous route to Bangladesh.
Sy urged the international community to "respond very urgently at the scale and magnitude that is required to alleviate the human suffering and also save lives."
His comments came ahead of Myanmar leader Aung San Suu Kyi's first visit Thursday to Rakhine since the crisis began.
The Nobel peace prize laureate who leads Myanmar's pro-democracy party has been hammered by the international community for failing to use her moral authority to speak up in defence of the Rohingya.
The Rohingya are loathed in Buddhist-majority Myanmar, where they are denied citizenship and denigrated as illegal "Bengali" immigrants.
The UN says the crackdown on them is likely tantamount to ethnic cleansing, while pressure has mounted on Myanmar to provide security for the Rohingya and allow people to return home.
But Sy said the IFRC was bracing for a drawn-out crisis.
"We have definitely to project ourselves into a longer future, and it is very difficult to see how long that future will be, but definitely not six months, definitely not even one year," he said.