The city of Beira from Mozambique, hit by cyclone, has confirmed her first death by cholera, as the incidence of the disease has jumped to 517.
To manage the infection, emergency clinics were established across Beira, a city of 500,000, said Mozambican national health director, Ussene Isse, according to TVM broadcaster.
The outbreak of acute disease has dramatically increased since the first five cases were confirmed last week.
The Idai cyclone severely damaged the water system for Beira when it was struck on March 14.
Approximately 900,000 cholera vaccine doses were expected to arrive on Monday, according to the World Health Organization.
Coles are spread by water and contaminated food.
It can kill within hours but is relatively easy to treat.
A general cyclone death toll in Mozambique is now 518.
With 259 deaths in Zimbabwe and 56 in Malawi, the three-country death toll is more than 815.
Authorities are warning that the tolls are preliminary as flood waters flood and reveal more bodies.
The Chinese government has sent doctors and emergency workers to fight the cause of cholera in Beira and Chinese support workers who have injected anti-golera disinfectant in parts of the port city.
US military joined international humanitarian aid efforts to Mozambique by transporting food and relief supplies from South Africa.
Poor, poor Beira neighborhoods are at particular risk.
Doctors Without Borders has said that it sees some 200 likely cholera cases a day in the city, where relief workers are rushing to restore the damaged water system and bring additional medical assistance.
Colera is a major concern for the hundreds of thousands of cyclone survivors in the South African nation who are now living in unclean conditions in camps, schools or homes that have been damaged.
Some drink from contaminated springs or dirty water, still.
As health personnel stress the need for better disease surveillance, the UN's deputy humanitarian coordinator in Mozambique, Sebastian Rhodes Stampa, has said that all cases of diarrhea are treated as being cholera.
Colera is endemic to the region, and "it breaks out quickly and is traveling very quickly," he told reporters.
Doctors Without Borders have said that other cases of suspected golera have been reported outside Beira in the Buzi, Tica and Nhamathanda areas that have been poorly hit, but the chances of spreading in areas less rural because people are more dispersed.