Labour shortages and disrupted cross-border trade caused by the deadly Ebola outbreak have sparked “grave food security concerns” in the worst-hit countries, the United Nations says.

Restrictions on movement in Guinea, Liberia and Sierra Leone has led to panic buying, food shortages and severe price hikes, especially in towns and cities, the UN’s Food and Agriculture Organisation said on Tuesday.

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“Access to food has become a pressing concern for many people in the three affected countries and their neighbours,” said Bukar Tijani, FAO Regional Representative for Africa.

The Ebola virus causes diarrhoea and internal and external bleeding.

“With the main harvest now at risk and trade and movements of goods severely restricted, food insecurity is poised to intensify in the weeks and months to come.

“The situation will have long-lasting impacts on farmers’ livelihoods and rural economies.”

The Ebola outbreak has killed 1,552 people and infected 3,062, according to the latest figures released by the World Health Organisation (WHO).

At current infection rates, the WHO fears it could take six to nine months and at least $US490 million ($A530.16 million) to bring under control, by which time over 20,000 people could be affected.

Quarantine zones imposed in the epicentre of the outbreak straddling the three countries will lead to food shortages for “large numbers” of people, the FAO said, with the main harvest season for rice and maize just weeks away.

Production of cash crops like palm oil, cocoa and rubber is also expected to be seriously affected, throwing people further into poverty.

Guinea, Liberia and Sierra Leone rely heavily on imports for cereals and other commodities.

The closure of border crossings where the three countries meet, as well as reduced trade at seaports, is strangling supply and sending prices soaring, the FAO said.

In Liberia, which has been hardest-hit by the outbreak with 694 deaths, the government has denied permission for any crew to disembark from ships docking at any of the country’s four ports.

In the Redlight Market, in the capital Monrovia, the price of cassava went up 150 per cent within the first weeks of August, the FAO said.

“Even prior to the Ebola outbreak, households in some of the affected areas were spending up to 80 per cent of their incomes on food,” said Vincent Martin, Head of FAO’s Resilience Hub in Dakar, Senegal.

“Now these latest price spikes are effectively putting food completely out of their reach. This situation may have social repercussions that could lead to subsequent impact on the disease containment.”

The UN’s World Food Program (WFP) has launched a regional emergency operation to get 65,000 tonnes of food to 1.3 million people in the worst-hit areas.

“Preventing further loss of human life and stopping the spread of the virus remain the top priorities at this time,” the FAO said.