Yaounde, Cameroon (CNN) -- Cholera has killed 297 people in the west African nation of Cameroon, health officials said Wednesday.
The outbreak, which began in May, has exceeded 3,000 cases, said Dr. Eric Mintz, the leader of the Centers for Disease Control and Prevention's global water sanitation and hygiene epidemiology team. The agency has an office in Cameroon.
"It's a lot of cases and a lot of deaths," he said in a telephone interview. "More deaths than should be expected under the best of conditions."
Under ideal conditions, cholera's fatality rate ought to be less than 1 percent, he said. But Cameroon's conditions are not ideal. Many people live far from the medical aid that could help them rehydrate and replace the sodium and potassium lost in their stools and vomit. "That delay can be critical," Mintz said. "If you don't get the fluids and the electrolytes replaced through hydration, you can go into shock and die as a result."
The country's northern region has been particularly hard hit. Three of 10 prisoners diagnosed with cholera at Maroua Central Prison in the far north were among the dead, the officials said.
CDC's Mintz said the rugged and remote region has been affected repeatedly by cholera epidemics, most recently last year.
About 70 percent of people living in the country's far north, bordering Nigeria and Chad and the Central African Republic, do not have access to potable water, according to a Ministry of Water and Energy official. Sanitation is also limited in the area and recent flooding has aggravated the situation.
The affected area is home to some 5 million people, according to UNICEF.
Outbreaks are now also occurring across the border in parts of Nigeria, Mintz said. "There's a lot of people crossing over the border all the time," he said. "So it's not surprising that the cholera is also crossing over the border."
The U.N. children's agency said it has dispatched emergency medical kits containing surgical gloves, water treatment tablets, cholera medicine, oral rehydration salts and educational materials. It said children are especially vulnerable to the disease.
Cholera is spread via the oral-fecal route, through water contaminated with human waste. "What puts people at risk is a lack of safe drinking water," Mintz said.
Boiling the water or treating it with chlorine or filtration or some other method to remove the contaminants can make it safe.
Untreated, cholera can kill within hours, according to the World Health Organization. Worldwide, as many as 120,000 people die each year from cholera.
CNN's Tom Watkins and Journalist Moki Kindzeka contributed to this report.