Haiti recorded nearly 800 cases of cholera the week after it was ravaged by Hurricane Matthew, the World Health Organization (WHO) said Wednesday, as health officials grapple to contain the disease.

There had been previous indications that Matthew triggered a surge in new cases but conclusively testing samples had been difficult in the aftermath of the storm, WHO's representative in Haiti, Jean-Luc Poncelet told reporters in Geneva.

With the testing system operational again, health officials have confirmed "the majority of suspected cases," Poncelet said.

Citing ministry of health figures, he said 773 cases had been registered between October 9 and 15.

The UN has previously announced it was sending a million cholera vaccines to the impoverished Caribbean nation to try to control the epidemic.

Since Haiti was devastated by an earthquake in 2010, around 10,000 people have died of cholera. The number of active cases surged to 300,000 in 2011, but had been brought below 30,000 in recent years.

Before Hurricane Matthew struck in the first week of October, more than 28,000 cases of cholera had been recorded this year.