BHUBANESWAR, India, Sept 3 (Reuters) - A cholera outbreak has killed at least 119 people in eastern India since August, health officials said on Monday, but an aid agency said the death toll was more than double that figure. More than 5,000 people infected with the bacterial disease in Orissa state had been treated, officials said. Nearly all the sick are poor, tribal people -- among the most neglected groups in India -- who caught the disease from eating bad meat or drinking polluted water. Cholera can cause its victims to expel massive amounts of water from their bodies through diarrhoea and vomiting, and can kill within days if the patient fails to take in plenty of fluids. It does respond to antibiotics. "This is an outbreak and not an epidemic," said Usha Patnaik, the director of health services in Bhubaneswar, the state capital. Authorities said the outbreak was slowly coming under control. But ActionAid, an international aid agency working in the area, said the local government was under-reporting the death toll to minimise the amount of compensation to be paid out to the families of the dead. "If the government reveals the true figure, they would have to offer compensation to many more families," Bratindi Jenna, ActionAid's manager in Orissa, said in a statement. ActionAid says at least 250 people have died from the disease. The local government rejects ActionAid's claims. ActionAid said cholera and diarrhoea outbreaks are common in the region, killing about 50 people every year.