Food, water and blankets have reached Guyana, a month after the Latin American country was hit by the worst floods in its history.
About 40% of people have lost some or all of their possessions
The shipment from the UN World Food Programme and Chile came on Thursday, as the death toll from disease rose.
The UN said more than 300,000 people - 40% of the population - have lost some or all of their possessions and it appealed for almost $3m (£1.6m) in aid.
It said the international response had been slow because of the Asian tsunami.
Six people were killed at the height of the January rains and almost 100,000 are still living in water-logged homes, officials say.
About 20 people are already thought to have died from the waterborne disease leptospirosis.
Health workers fear the deadly bacterial infection, which breeds on water contaminated with animal carcasses and sewage, could spread more widely.
Health Minister Leslie Ramsammy said antibiotics were being distributed in an attempt to contain the outbreak.
Dengue fever, malaria and diarrhoea are also a danger.
Col Chabilall Ransarup, head of Guyana's civil defence commission, told the BBC that at least 10 communities along the densely populated and impoverished eastern coast were still knee-deep in stagnant water.
Rice crops, roads and drainage systems have been damaged
Jan Egeland, the UN emergency relief co-ordinator, said: "The emergency may have gone unnoticed outside Guyana in the aftermath of the tsunami.
"But for those struck, the effects of the floods have been no less devastating than on the Indian Ocean beaches."
The BBC's Iain Bruce, in the capital Georgetown, says Guyana is still reeling from the floods.
In the longer term, he adds, with drainage systems, roads and rice crops all devastated, Guyana's frail economy looks set for a further battering.