The state's top health bureaucrat said the cholera outbreak was caused by locals drinking from stagnant pools of water and eating contaminated meat.
"Diarrhoea is a seasonal problem. But in our case the situation is severe," said Orissa health secretary Chinmoy Basu.
"The tribals have particular food habits like eating uncooked meat, not drinking water from tube wells. So health and hygiene are also factors."
Locals also say they are forced to consume water from streams dirtied every summer by monsoon rains.
The disease outbreak began last week in the poor districts of Rayagada and Koraput, 500 kilometres (310 miles) southwest of the state capital Bhubaneswar, officials said.
A doctor at the main community health care centre in the Kashipur area, where the outbreak in Rayagada district has been concentrated, said 51 people were dead and more than 3,000 were under treatment.
In neighouring Koraput, an official said at least 54 people had died from cholera and mroe than 3,000 people were being treated for water-borne diseases in one area.
Local leaders of what are known as tribal communities in India have said at least 200 people have died.
A lawmaker for Kashipur in the state assembly blamed the severity of this year's outbreak on the state's failure to supply clean water and adequate health care.
"With a total population of close to 150,000 (in both districts) there are only three regular government doctors, which means there's a lone doctor to treat a population of 50,000," said lawmaker Anantram Majhi.
Medical teams have been dispatched to both districts to make up for the shortage of local doctors.
In spite of the large numbers of people dead from the disease, Orissa Chief Minister Naveen Patnaik denied the state was facing any epidemic.
"The situation is under control. The administration is taking every possible steps to counter cholera," he told reporters. "Dont call it an epidemic."