UNITED NATIONS, April 1 (Xinhua) -- Humanitarian aid workers in areas ravaged by Cyclone Idai are fighting to stave off the spread of cholera, establishing 11 treatment centers in Mozambique alone, a UN spokesman said on Monday.

Of those 11 sites, nine are operational, including in the hard-hit port city of Beira, said Stephane Dujarric, spokesman for UN chief Antonio Guterres.

"A cholera vaccination campaign will begin on this Wednesday," Dujarric said. "Some 258 cases have been reported in the last 24 hours. There is also a high-risk of the spread of vector-borne diseases, with 276 malaria cases also reported in the affected areas."

Cholera, spread by contaminated food and water, causes diarrhea that can result in death if not treated.

The number of confirmed deaths in areas suffering from Idai, parts of Malawi, Mozambique and Zimbabwe, has topped the 700 mark, with Mozambique itself reporting 501 fatalities.

The president of Zimbabwe, Emmerson Mnangagwa, said shortly after the cyclone struck late on March 14 that he feared 1,000 dead from the storm. So far about 180 fatalities have been confirmed in Zimbabwe.

Officials have said the toll may never be known because many bodies have been buried, without registration, many in shallow graves and many of those corpses have washed out to sea, as have many others from the flooding rains accompanying Idai.

"The Economic and Social Council will convene a Special Meeting on the response to Cyclone Idai in Mozambique, Malawi and Zimbabwe," said the spokesman.

"Deputy Secretary-General Amina Mohammed will address the meeting, as well as Emergency Relief Coordinator (Under-Secretary-General) Mark Lowcock," Dujarric told reporters during a regular briefing, adding that the meeting will be held on Tuesday.

"The meeting will discuss how to support a well-coordinated response, focusing on immediate humanitarian needs, as well as sustainable and risk-informed medium- and long-term recovery and reconstruction in the aftermath of the storm," Dujarric said.