Almost 900 people are thought to have died when the storm battered the island
Haiti is beginning three days of national mourning for the hundreds of victims of Hurricane Matthew, amid a developing humanitarian crisis.
Almost 900 people died when the storm battered Haiti, and with outbreaks of cholera in the aftermath at least another 13 have now also lost their lives.
About 60 more have contracted the disease, the head of the Haitian health ministry's cholera programme said.
Christian Aid say the situation is "critical" - and was likely to remain that way for 18 months.
Prospery Raymond from the charity said: "The south part of Haiti is really affected by Hurricane Matthew.
"The population are really in need of water, shelter, materials. Compared to the earthquake this emergency is very, very critical."
Ireland is to provide humanitarian aid to Haiti in response to the hurricane.
While UNICEF Ireland has launched an emergency appeal for the children of Haiti - after assessments indicated they need US$5m to carry out essential life-saving work.
It says the heavy winds of up to 140km/h and flooding damaged homes, schools and health centres.
"Basic social services, already fragile before Matthew, are now mostly wiped out.
"Trees and crops are gone in many places, which will likely result in food insecurity and a spike in child malnutrition", UNICEF adds.
It comes as 11 people are known to have died in Georgia, North Carolina and Florida after Matthew tore across the southern US states.
North Carolina's Governor Pat McCrory said: "This is a very, very serious and deadly storm."
In Fayetteville, the National Weather Service said 8.5 inches of rain had fallen in about 12 hours.
Heavy rainfall last week had already caused the ground to become saturated.
Two people were killed in Bulloch County, Georgia, by falling trees.
US President Barack Obama has declared emergencies in North and South Carolina, Florida and Georgia and ordered that federal aid be provided.
He has also spoken to the four states' governors.
The eye of the storm had remained offshore until it made landfall near the town of McClellanville in South Carolina.
It also hit Myrtle Beach in South Carolina and Wilmington, North Carolina.
There was flooding in the historic town of Savannah, Georgia, and in Charleston, South Carolina.
The storm's winds, though, had dropped to around 75mph, way below the 145mph recorded when it bore down on Haiti.