The United Nations has said for the first time that it was involved in the introduction of cholera to Haiti and needs to do "much more" to end the suffering of those affected, estimated at more than 800,000 people.
Researchers say there is ample evidence that cholera was introduced to Haiti's biggest river in October 2010 by inadequately treated sewage from a UN peacekeeping base.
The United Nations has never accepted responsibility, and has answered lawsuits on behalf of victims in US courts by claiming diplomatic immunity.
UN deputy spokesman Farhan Haq's statement referring to the UN's "own involvement", which was sent to the Associated Press on Thursday, came a step closer to an admission of at least some responsibility and was welcomed by lawyers for the victims.
"This is a major victory for the thousands of Haitians who have been marching for justice, writing to the UN and bringing the UN to court," said Mario Joseph, a Haitian human rights lawyer whose law firm has led a high-profile claim on behalf of 5,000 cholera victims who blame the UN for introducing the disease.
In a decision issued late on Thursday, a US federal appeals panel in New York upheld immunity for the UN and affirmed a lower court's 2015 judgment dismissing that case. Cholera victims and their lawyers have 90 days to decide if they will seek an appeal with the US Supreme Court.
Meanwhile, Mr Haq said that the United Nations has been considering a series of options, and "a significantly new set of UN actions" will be presented publicly within the next two months.
He told reporters later that a UN-appointed panel had already looked into the UN's involvement.
It found that a local contractor failed to properly sanitise the waste at the UN base.
"We've been trying to see exactly what we can do about our own particular role as this has been going on" and how "to bring this outbreak to a close", he said.
Mr Haq would not say whether reparations were under consideration.
His statement on UN involvement was first reported by The New York Times.
Five UN human rights experts criticised the United Nations in a letter to top UN officials late last year for its "effective denial of the fundamental right of the victims of cholera to justice".
At least one lawsuit was dismissed because of the UN's diplomatic immunity claim.
Mr Haq reiterated that the UN's legal position in claiming diplomatic immunity "has not changed".
According to government figures, cholera has affected more than 800,000 people, or about 7% of Haiti's population, and has killed more than 9,200. As of March, it was killing an average of 37 people a month.
Haiti is the poorest country in the Western hemisphere and only 24% of Haitians have access to a toilet. Sewage is rarely treated and safe water remains inaccessible to many.
At a dusty crossroads on the outskirts of Haiti's capital, Port-au-Prince, local residents gathered at a rubbish-clogged stream to wash clothes and bathe.
"So now they are going to find a way to clean the disease from the country? It's been here for years and it seems like it is here to stay," said worker Jhony Nordlius as he pushed a wheelbarrow past a fetid canal where children were splashing and collecting rubbish.
Maxcilus Vale, who ekes out a living shining shoes by the waste-clogged waterway, was more hopeful about the UN's statement.
"Maybe now we'll get more sanitation and water treatment to help make cholera go away. I hope so because it has harmed many people," said Mr Vale, as he washed his socks in a roadside pool of stagnant water.
Researchers said cholera was first detected in the central Artibonite Valley and cited evidence that it was introduced to Haiti's biggest river from a UN base where Nepalese troops were deployed as part of a peacekeeping operation which has been in the country since 2004. Cholera is endemic in Nepal.
In December 2012, UN secretary-general Ban Ki-moon announced a 2.27 billion dollar (£1.72 billion) initiative to help eradicate cholera in Haiti and neighbouring Dominican Republic, which share the island of Hispaniola, but the ambitious 10-year plan is underfunded. According to a report last November, only 307 million dollars (£233 million) has been received.
Mr Haq said the announcement of UN plans for new action to address cholera was made in response to a draft report by the UN special investigator on extreme poverty and human rights.
Ahead of its release, likely to be in late September, he said "we wanted to take this opportunity to welcome this vital report".
Mr Haq said its findings and recommendations "will be a valuable contribution to the UN as we work towards a significantly new set of UN actions".