Haiti's desperate earthquake survivors faced a new deadly threat on Friday as the United Nations reported a rise in cases of diarrhea, measles and tetanus in squalid tent camps for victims.

A vast foreign aid effort is struggling to meet survivors' needs 17 days after the disaster, which killed about 170 000 people and left one million homeless and short of food, water and medical attention.

And with medicine running low amid efforts to treat hundreds of thousands of injured and homeless cramped into makeshift camps, officials and aid groups are scrambling to avoid a potential public health calamity that could push the death toll higher.

"Several medical teams report a growing caseload of diarrhea in the last two to three days," World Health Organisation spokesperson Paul Garwood said.

"There are also reports of measles and tetanus, including in resettlement camps, which is worrisome due to the high concentration of people," he told journalists in Geneva.

UN agencies and Haiti's government aim to launch a vaccination campaign against measles, tetanus and diphtheria next week. Just 58% of Haitian infants were immunised before the quake, Garwood said.

He highlighted a "critical" need for surgeons, with an estimated 30 to 100 amputations being carried out every day in some hospitals, while supplies of anesthetics and antibiotics were also needed.

The 7-magnitude quake on January 12 decimated Haiti's already meager health system, creating conditions for disease to thrive in the cramped refugee camps.

Only one person in two among the Haitian population of more than nine million people has access to clean drinking water, and only 19% have decent sanitation.

On Friday, Ecuadoran President Rafael Correa became just the second foreign leader to visit Haiti since the quake, lending his voice to international calls for more emergency relief and assistance with reconstruction.

"This is a tragedy, a humanitarian tragedy. Haiti at this moment represents the pain of victims but also hope," Correa said.

He also highlighted what he called the "imperialism" of aid efforts, echoing criticism leveled by other leftist Latin American leaders.

"There is a lot of imperialism among the donors. They donate first, but most of it goes back to them," he said at a joint press conference with Haiti's President René Préval.

Without naming specific programs, he criticised both military relief efforts and those of foreign non-governmental organisations.

Haitians living in sprawling makeshift camps in the ruins of Port-au-Prince and elsewhere complain that the flood of international aid arriving in the country is trickling down too slowly.

Many are trying to rebuild their lives, with marketplaces springing up on streets around the capital, although business is tough.

"It's very hard -- there aren't many buyers, but there are lots of sellers," said 24-year-old Rose Gardy-Joseph, sitting next to a basket full of colourful sweets, soft cheese and napkins.

But survivors also face rising insecurity, with thousands of criminals on the loose after the main jail collapsed in the quake and reports of rape and violence plaguing the weak and vulnerable.

The deputy head of the UN mission in Haiti, Anthony Banbury, said the United Nations did not want huge tent cities later turning into slums where there was poor sanitation, no security and child abuse.

The United Nations, along with aid agencies and security forces, must "do things smart, as well as fast, and that's a big challenge for us now", Banbury said.

The US State Department said it was spearheading a coordinated effort together with Unicef, the Haitian government, the Red Cross and other agencies to combat the potential trafficking of children.

The aid effort has also been dogged by complaints over a lack of coordination between UN officials, the 20 000 US forces in Haiti, and a swarm of aid groups helping the country.

There were no signs of further survivors beneath the rubble after a 16-year-old girl was pulled alive from the ruins on Wednesday after surviving 15 days without any food or water.

Rebuilding the Western hemisphere's poorest nation could take decades, said Edmond Mulet, the acting head of the UN mission in Haiti, whose predecessor was killed in the quake.

"I think this is going to take many more decades than only 10 years and this is an enormous backwards step in Haiti's development. We will not have to start from zero but from below zero," Mulet told the BBC. - AFP