UNITED NATIONS (AP) - The United Nations rejected a claim for damages on behalf of more than 5,000 Haitian cholera victims and their families on Thursday, citing diplomatic immunity. The claim was filed in November 2011 by the Institute for Justice and Democracy in Haiti, a Boston-based human rights group that contended the U.N. and its peacekeeping force are liable for hundreds of millions of dollars for failing to adequately screen peacekeeping soldiers. It cited studies suggesting that the disease was inadvertently brought to Haiti by a U.N. battalion from Nepal, where cholera is endemic. A local contractor failed to properly sanitize the waste of a U.N. base, and the bacteria leaked into a tributary of one of Haiti's biggest rivers, according to one study by a U.N.-appointed panel. Cholera has sickened nearly 500,000 people and killed over 7,750 people since the outbreak began in October 2010, according to the Haitian government. About half the people in the country of 10 million have no bathroom at all and sanitation access is the worst in the Western Hemisphere. U.N. spokesman Martin Nesirky said the United Nations informed representatives of the claimant of the U.N. rejection on Thursday. Secretary-General Ban Ki-moon also called Haitian President Michel Martelly to inform him of the decision "and to reiterate the commitment of the United Nations to the elimination of cholera in Haiti," Nesirky said. Brian Concannon, the institute's director, said that after 15 months, the rejection was a single sentence based on the world organization's immunity. "We're disappointed more than surprised, but this is the typical U.N. response to claims of large-scale harm by their operations," he told The Associated Press. We're disappointed because the U.N. is passing up a chance to stop cholera's killing, and to show leadership in promoting the rule of law. Concannon, an attorney, said the institute's next step will be to go to a national court to seek compensation for the victims, "but we haven't decided which one yet," possibly in Haiti, the United States or Europe. The institute was seeking a minimum of $100,000 for each bereaved family and $50,000 for each cholera survivor. When the compensation claim was filed with the secretary-general and the claims unit for the U.N. peacekeeping mission in Haiti in 2011, Concannon said he hoped the U.N. peacekeeping force would create a lifesaving program that would provide sanitation, potable water and medical treatment. He also said he wanted a public apology for the victims. In December, Ban announced a $2.27 billion initiative to help eradicate cholera in Haiti and the Dominican Republic, which share the island of Hispaniola, and vowed to work aggressively to secure donations for the ambitious but still mostly unfunded 10-year plan. Nesirky said Thursday that the secretary-general "again expresses his profound sympathy for the terrible suffering caused by the cholera epidemic, and calls on all partners in Haiti and the international community to work together to ensure better health and a better future for the people of Haiti."