A cholera outbreak in Zimbabwe has killed at least 484 people since August, according to the UN.
More than 11,700 cases of cholera have been recorded over the same period, an update from the UN office for humanitarian affairs said.
The cholera outbreak has affected most of Zimbabwe's regions.
Its spread has been aided by the collapse of Zimbabwe's health and sanitation systems amid a prolonged economic and political crisis.
Previously it had been reported that 425 people had died from cholera, which is spread by contaminated water.
State media has reported that much of the capital, Harare, has been left without water because of a shortage of purification chemicals.
The World Health Organization has warned that the outbreak "can spread quickly into areas without access to safe water and sanitation".
"Case fatality rates may rapidly escalate in populations without rapid access to simple treatments," it said.
Cholera is endemic in Zimbabwe, and there have been outbreaks annually since 1998, according to the WHO.
But this is the most deadly outbreak for 15 years, health officials say.
During the outbreak, the case fatality rate from cholera has risen to 4%, the WHO said, but had reached 50% in some areas during its early stages.
Health Minister David Parirenyatwa has said people should stop shaking hands to prevent the disease spreading.
Cholera can be treated easily but hospitals lack medicines and staff.
The WHO said Zimbabwe's health facilities face a "massive gap" in required medicines due to a drop in local manufacturing capacity, weakened in turn by a shortage of foreign currency.
"Reactivating primary health care services should keep being addressed as a matter of emergency," the health agency said.
Cases of cholera have been reported either side of Zimbabwe's borders with South Africa, Botswana and Mozambique, showing the sub-regional threat of the outbreak, it said.
The BBC's Peter Biles reports from the South African town of Musina, near the border with Zimbabwe, that cholera patients are being treated at an emergency centre on the lawn in front of the hospital.
One cholera victim from Harare told him that on Zimbabwe's side of the border, toilets had not functioned for one month, and people were "defecating everywhere".
"We need the world to help us. The country is dying and people are dying."
South Africa's ministry of health has confirmed more than 160 cholera cases, including three deaths.
Zimbabwe's government has blamed its crisis on Western sanctions it says are aimed at trying to bring down President Robert Mugabe.
But the sanctions imposed after allegations of electoral fraud and political violence are aimed at Mr Mugabe and his close associates and consist of travel bans and a freeze on their foreign assets.
Zimbabwe is facing a severe economic crisis.
The latest estimated annual inflation rate was 231,000,000%, and just one adult in ten is thought to have a regular job.
Appeal for funds for Zimbabwe cholera epidemic