Cholera is spreading to rural areas making the disease harder to contain
More than 60,000 people in Zimbabwe have now been infected by cholera, the World Health Organization (WHO) says.
This figure had been described by the UN's health agency and other agencies as being the "worst case scenario" in the epidemic which broke out in August.
Cholera has now claimed the lives of more than 3,000 people in Zimbabwe.
The epidemic of the disease, which broke out in August 2008, has been fuelled by the collapse of Zimbabwe's water, sanitation and health systems.
Many hospitals have shut down and most towns suffer from poor water supply, broken sewers and uncollected waste.
Aid workers fear the rainy season could lead to even more infections as water sources become contaminated.
Health experts estimated late last year that 60,000 cases of cholera in Zimbabwe would be a worst-case scenario.
But, in latest figures released by the WHO in Geneva, some 60,401 Zimbabweans now have the disease. The death toll stands at 3,161.
STATE OF ZIMBABWE
Five million people - almost half population - need food aid
Central bank introduced Z$100tr note, worth about US$30 (£20)
Unemployment more than 80%
Nearly 3,000 people dead in cholera outbreak
Many teachers, doctors and nurses not working
The UN agency said the outbreak "showed no signs of abating" and called for urgent action from the international community to help tackle the situation.
"We are dealing with an extraordinary public health crisis that requires from us all an extraordinary public health emergency response, and this must happen now before the outbreak causes more needless suffering and death," the WHO's Dr Eric Laroche said.
The epidemic has been exacerbated by the political and economic problems facing Zimbabwe.
Many medical staff have been refusing to work unless they get paid in hard currency, because the value of the Zimbabwean dollar is virtually worthless.
The charity Medecins Sans Frontieres told the BBC last week that the disease was spreading to remote areas, making its containment much harder.
President Robert Mugabe has faced increasing criticism over his country's dire economic and humanitarian plight.
But his allies have accused Western countries of trying to use the cholera outbreak as an excuse to topple him.