Homes, schools and crops were destroyed and now children are starting to get sick.
Health officials are concerned that the disease is spreading as flood waters mix with sewage.
The hurricane lashed Florida on Friday with howling winds and rumbled northward up the U.S. Atlantic coast.
Matthew was the strongest storm to slam Haiti in more than 50 years.
The U.N. has accepted partial responsibility in Haiti's 2010 cholera crisis.
The waterborne disease has killed more than 9,000 people since the earthquake in 2010.
Fears of violence as President Michel Martelly ends his term with nobody elected to replace him.
Pierre Louis Opont, president of Haiti's electoral council, said the runoff vote was being pushed back for security reasons.
Dominican authorities are poised to expel by force thousands of undocumented Dominicans of Haitian descent.
Libraries Without Borders aims to promote culture and knowledge in disaster zones.
An outbreak that has killed more than 8,300 people has been traced to U.N. peacekeepers