Humanitarian officials say the death toll from a cholera outbreak in Sierra Leone has risen to 217 people.

Oxfam said Thursday that the death rates in the West African country are almost double emergency thresholds.

Nearly 12,000 cases already have been reported and Oxfam said the number of people affected is "likely to increase significantly in the next month."

Aid groups say there has been a spike in reported cholera cases since mid-July and the onset of the rainy season.

Some 82 deaths have been reported in neighboring Guinea, while other cases have been seen in Mali and Niger.

Cholera is an infection of the small intestine, contracted by eating or drinking contaminated food or liquids. It can cause acute diarrhea and vomiting and can kill within hours.