Cyclone Idai, the "worst humanitarian disaster in Mozambique", has killed at least 468 people and affected 1.85 million.
The number of confirmed cholera cases in cyclone-ravaged Mozambique climbed sharply to 139 Thursday as authorities prepared to roll out a mass vaccination campaign to stem the spread of the deadly disease.
"The total number of cholera cases is now 139," government health officer Ussein Isse told AFP.
President Filipe Nyusi on Thursday told a news conference authorities had called off rescue operations for victims of the deadly cyclone which tore through the central parts of the country on March 15.
He described it as the "worst humanitarian disaster in Mozambique".
The storm killed at least 468 people and affected 1.85 million.
He said 945 rescuers had taken part in the two-week long search and rescue operation.
"We thank all of them. They are heroes," he said.
World Health Organization official David Wightwick said mass cholera vaccinations would start next week.
The country is awaiting the delivery of 900,000 doses of vaccines expected in the country on Monday.
Officials said the vaccination campaign will be launched from Wednesday to stem the spread of the disease, which thrives in conditions of poor hygiene and causes acute diarrhoea that can be fatal if untreated.
Wightwick told reporters in Beira that nine cholera treatment centres were being set up around the central Sofala province, which bore the brunt of the cyclone.
The UN said in a statement that authoritities have already reported "some 2,500 cases of acute watery diarrhoea".
900,000 vaccine doses
Experts have warned that the destruction of drinking water sources and lack of sanitation in overcrowded shelters in Mozambique could create breeding grounds for waterborne diseases such as cholera.
The vaccinations will protect the tens of thousands of survivors for around three months, he said.
"It buys us some time and it means we will probably have to do a further vaccination," Wightwick said.
"The first objective is to control the outbreak," he said, warning that "there are other places that remain cut off".
A cholera prevention publicity campaign has also been launched with messages via radio and loudhailers across affected towns and villages.
Cyclone Idai smashed into Mozambique nearly two weeks ago, unleashing hurricane-force winds and heavy rains.
It flooded much of the centre of the poor southern African country and then battered eastern Zimbabwe and Malawi.
UNICEF warned that there is "very little time to prevent the spread of opportunistic diseases".
It warned in a statement that current conditions of "stagnant waters, lack of hygiene, decomposing bodies (and) overcrowding in temporary shelters" could lead to outbreaks of diarrhoea, malaria and cholera, "to which children are especially vulnerable".
"The lives of millions of children and families are on the line, and we urgently need to mount a rapid and effective humanitarian response," said UNICEF chief Henrietta Fore.
She launched a $122 million (108 million euro) appeal for the three affected neighbouring countries.
"The massive scale of the devastation wrought by Cyclone Idai is becoming clearer by the day," she said.