The U.N. health agency World Health Organization said the outlook was bleak, as it seeks $640 million to fight the infectious disease, but said the longer it takes to ramp up the battle, the worse the situation will get.
"WHO estimates that a billion people across 43 countries are at risk of cholera," said Henry Gray, the agency's incident manager for the global cholera response.
So far this year, 24 countries have reported cholera outbreaks, compared to 15 by mid-May last year.
Countries that are not usually affected by cholera are being struck, and case fatality rates are far exceeding the typical one in 100.
Gray blamed the rise in cases on poverty, conflict and climate change, and the population displacement they trigger.
The WHO said vaccination campaigns had been severely hampered.
Oral cholera vaccine is a case in point: over 18 million doses have been requested this year but only eight million have been made available and so prevention campaigns have been stopped.
Rather than the full two doses, only one is being issued to recipients "to try to spin it out,", said Gray.
"The outlook is bleak."
WHO wants $160 million for more than 40 countries over the next 12 months. It is working in coordination with the U.N. children's agency UNICEF, which wants $480 million.
Jerome Pfaffmann Zambruni, UNICEF's public health emergency unit chief, noted that back in November, the agency had asked for $150 million for cholera response -- a figure now eclipsed as the situation has worsened.
"It's a wake-up call," he told a briefing in Geneva.
Cholera is contracted from a bacterium that is generally transmitted through contaminated food or water.
It causes diarrhea and vomiting, and can be especially dangerous for young children.
"There is a pandemic killing the poor right in front of us and we know exactly how to stop it but we need more support and less inertia from the global community because if we don't act now, it's going to get worse," he said.
