PORT-AU-PRINCE: A US federal appeals court has upheld the United Nations' immunity from a damage claim filed on behalf of 5,000 cholera victims who blame the UN for an epidemic of the deadly disease in Haiti.

In a decision issued late Thursday, the US 2nd Circuit Court of Appeals in New York affirmed a lower court's January 2015 dismissal of a lawsuit brought in the worst outbreak of cholera in recent history.

"We have considered all of plaintiffs' arguments on appeal and find them to be without merit," the US appellate judges said.

The ruling came shortly after UN deputy spokesman Farhan Haq referred to the United Nations' "own involvement" in the introduction of cholera to Haiti.

It was a significant statement because the UN has for years kept silent about allegations its peacekeepers introduced cholera to Haiti. It has answered lawsuits on behalf of victims filed in US courts by claiming immunity under a 1946 convention.

Haq said in a statement that the UN needs to do "much more" to end the suffering of those affected and pledged that "a significantly new set of UN actions" will be presented publicly within the next two months.

But Haq reiterated that the UN's legal position in claiming immunity hasn't changed.

Brian Concannon, executive director of the Boston-based Institute for Justice and Democracy in Haiti, said advocates for Haitian cholera victims will be watching the UN's actions closely. They have 90 days to decide whether to file an appeal to the US Supreme Court.

"We will decide how to proceed based on whether the UN's actions fulfill the cholera victims' rights to an effective remedy," Concannon said in a statement.

Since its introduction to Haiti in October 2010, cholera has killed more than 9,300 Haitians and sickened over 800,000. It showed up some 10 months after a devastating earthquake in the south of Haiti, deepening the country's misery at a time when it was ill-equipped to cope with another crisis.

The waterborne disease is now considered "endemic" in Haiti, meaning it's an illness that occurs regularly.

Researchers say there is ample scientific evidence the disease was introduced to Haiti's biggest river by inadequately treated sewage from a base of UN peacekeepers from Nepal, one of the units that have rotated in and out of a multinational force in Haiti since 2004.