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By Stephanie Nebehay

GENEVA, Dec 9 (Reuters) - Up to 60,000 people in Zimbabwe could be infected with cholera in the worst case if the epidemic spirals further out of control, the World Health Organisation (WHO) said on Tuesday.

The known number people with cholera in Zimbabwe stands at 13,960 with 589 deaths, although the true extent of the outbreak which began in August is unclear, according to the U.N. agency.

"The health-cluster assessment in a worst-case scenario is 60,000 cases," WHO spokeswoman Fadela Chaib told a news briefing in Geneva.

The cholera outbreak is the worst recorded in Zimbabwe, where many patients are unable to reach health centres or if they do, find them unable to provide simple life-saving medicines, it said.

Cholera, an intestinal infection that spreads through contaminated food or water, can lead to severe dehydration and death without prompt treatment.

The highly contagious disease is both preventable and treatable under normal circumstances, but Zimbabwe's health sector has nearly collapsed as a result of the country's economic crisis.

The rate of fatalities is quite high -- 4.5 percent overall and up to 50 percent in some areas -- according to the WHO. It says it should be below one percent of cases in any outbreak.

The WHO is considering providing financial incentives for unpaid or underpaid health workers in Zimbabwe to return to their jobs, according to Chaib.

"Critical staff shortages are due to extremely low salaries. An incentive scheme is being finalised between the health cluster and ministry of health to attract workers, mainly nurses, back to their posts," she told Reuters.

The WHO, which has sent a high-level team to Harare, is working with dozens of aid agencies to get an accurate picture of infections in rural areas and combat the outbreak.

"It is total chaos, three hospitals in Harare are closed due to a lack of personnel," said Elisabeth Byrs, spokeswoman of the U.N. Office for the Coordination of Humanitarian Affairs (OCHA).

She also said security had become more tense and there had been reports of looting by crowds and of attacks on aid workers.

Some 5.7 million people -- almost half the population -- might need food aid by early 2009, she said, citing figures from the World Food Programme, a U.N. agency.

"Eighty percent of the population does not have access to safe water as a result of major shortages of water treatment chemicals...," UNICEF spokeswoman Veronique Taveau said.

UNICEF has drawn up a four-month emergency plan requiring $17.5 million to combat the crisis over the four next months in the water and sanitation, health, and education sectors. (For more information on humanitarian crises and issues visit www.alertnet.org) (Editing by Jonathan Lynn)

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