The Category four storm is believed to have killed as many as 900 people in the Caribbean country and a cholera outbreak is the next big concern.
The weakening storm barrelled up the US coast, killing at least 16 people.
It has now moved out to sea and is not expected to return to the shore.
Officials have warned people in North Carolina to stay at home and not take unnecessary risks.
The hurricane was the strongest to hit the region in a decade. It kept up its hurricane strength with winds of at least 110mph (177km/h) for seven days.
In Haiti, the poorest country in Latin America, it destroyed tens of thousands of homes, leaving more than 60,000 people staying in temporary shelters.
The UN's humanitarian co-ordinator in Haiti, Mourad Wahba, said: "We are not far from having one million people who are in urgent need of humanitarian assistance."
Crops were destroyed, putting pressure on food resources, and at least 13 people have died of cholera following widespread flooding, raising fears of an outbreak similar to that after the 2010 earthquake, when nearly 10,000 people died.
A health worker at a cholera treatment centre in the town of Jeremie, where up to 80% of buildings have been destroyed, said there were not enough beds for the patients who were coming in.
Other countries including France and the US have pledged to send aid. The Red Cross has launched an emergency appeal for $6.9m (£5.6m) and Unicef said it needed at least $5m to meet the immediate needs of 500,000 affected children.
But one aid worker said some people had started to put up blockades to try and stop aid convoys they saw driving through their areas without stopping.
Hurricane Matthew was downgraded to a post-tropical cyclone early on Sunday and the winds reduced to 75mph (121km/h) as it passed over south-eastern states of the US. But it still brought substantial damage, flooding cities and knocking out electric power to millions of homes and businesses. Two million people were ordered to leave their homes.
Of the 16 people who are so far known to have died, nearly half were in North Carolina. Some were swept away by floodwater while in their vehicles; some were killed by falling trees; some suffocated in carbon monoxide fumes from generators; and one elderly man was pinned to the ground by his electric wheelchair.
Four people have been reported missing in the city of Fayetteville in the state.
Fayeteville's Mayor Nat Robertson said: "Stay home. Most of your Church services have been cancelled. There's no reason to go out. Take the day off."
President Barack Obama has declared a state of emergency, meaning federal money can be sent to the affected states.
North Carolina's Governor Pat McCrory made a plea for people to turn their attention from the political news in the presidential debate to his state's plight.