Allegations that UN peacekeepers are the source of Haiti's cholera epidemic are being formally investigated by the organisation.
Despite weeks of denials by the UN and the World Health Organisation (WHO), there seems little doubt now that the deadly bacterium, which has left thousands of people sick or dead, was brought into the country by infected troops from Nepal, where the disease has broken out several times this summer.
The UN's previous dismissals of the claims were a primary factor in riots that paralysed parts of Haiti last week. At least three people were killed and dozens injured as unrest spread from the north to the capital last Thursday amid growing anger at the UN's defiance.
Relief efforts stalled last week as supplies and workers were held up by barricaded roads and closed airports. Gunshots were heard in Port-au-Prince, and police fired tear gas at angry demonstrators throwing rocks at UN vehicles on Thursday. As a result, Oxfam stopped distributing soap, hygiene kits and rehydration salts in Cap-Haitien, where the fatality rate is the highest in the country. Dr Unni Krishnan from Plan International said: "All the aid agencies have been affected by the violence and protests. This [Saturday] morning we are just starting to freely move our people and supplies because things seem a little quieter."
The UN investigation into the source of the epidemic comes after rumours of a "foreign disease" triggered fear and then anger among Haitians. The first confirmed cases have been traced along the Artibonite River, not far from the UN base which houses nearly 500 Nepalese guards. Locals have long complained about the stinking sewage oozing from the base, contaminating the river that they rely on for drinking water. UN military police were spotted last week taking samples from a broken pipe next to the base's latrines and an overflowing septic tank. The UN has belatedly agreed to review all its sanitation systems across Haiti, officials told Associated Press.
The latest Nepalese deployment arrived in October after summer's cholera outbreaks in Nepal. The UN's insistence that none of the peacekeepers showed symptoms of the disease has caused frustration among experts as 75 per cent of people infected with cholera are without symptoms but remain contagious. These denials came as aid agencies struggled to convince people about the need for good hygiene and sanitation regardless of disease symptoms.
The whole region could be at risk from the cholera strain, which the US Centers for Disease Control has confirmed matches the strain found most prevalently in South Asia. The first cases were recorded in neighbouring Dominican Republic and in Florida last week.
In a country plagued by drug wars, political coups, poverty and natural disasters, and which relies on foreign governments, aid agencies and the UN for almost everything, the implications of the UN investigation are far-reaching. The current peacekeeping mission is the fifth since 1993, and rumours of a UN cover-up could even threaten the country's fragile stability, according to Brian Concannon, the director of the Institute for Justice and Democracy in Haiti. "The way to contribute to public anger is to lie," Mr Concannon said.
Amid the growing security threat, which is likely to intensify before next Sunday's planned elections, Médecins Sans Frontières pleaded yesterday for more nurses and doctors in Haiti as they prepare to treat twice as many new cases this week.
The disease is expected to peak between 26 and 29 November in the northern slum areas of Cité Soleil, where the disease entered the capital three weeks ago, according to MSF epidemiologists. This means the organisation's already overstretched health professionals are likely to see between 300 and 400 new patients from Cité Soleil every day this week – up from 220 a day last week.
The number of cases in Martissant, an equally unsanitary slum in a southern district of Port-au-Prince, has risen by nearly 40 per cent in the last few days. To stand any chance of coping, MSF, which is providing more than 80 per cent of all medical help for cholera patients, must increase the number of cholera beds from 1,900 to 3,000 over the next few days.
Stefano Zannini, the head of the MSF mission in Haiti, said: "By next weekend we will start to see the first peaks of cholera, which will continue nationally over the next few weeks. The next 10 days are critical and there are not enough health professionals to cope. We are taking drastic steps and appealing to any nurses, doctors and auxiliaries in Haiti who are not in employment to come and help us. We want the Health Ministry to make final-year medical students available as well. And we need doctors and nurses internationally to make themselves available for Haiti now."
The UN has received only $5m (£3m) in response to an appeal more than a week ago for $164m to tackle the epidemic. Agencies such as ActionAid are redirecting money meant for rebuilding and employment programmes, gathered after January's devastating earthquake, to health education campaigns. There are signs that these messages are starting to filter through, but millions of Haitians who are surviving on less than $2 a day still have no access to clean water, bleach and toilets, said Jane Moyo from ActionAid.
For the doctors on the cholera frontline, aid agencies have woken up too late. Mr Zannini said: "Haiti is full of humanitarian organisations. But if you are a humanitarian organisation how can it take you so long to respond to a crisis which started five weeks ago? That we cannot understand. We have been trying to fight a fire with a glass of water."