DAKAR, Senegal — A fierce cholera epidemic is spreading through the coastal slums of West Africa, killing hundreds and sickening many more in one of the worst regional outbreaks in years, health experts said.

By ADAM NOSSITER (from nytimes.com)

Cholera, transmitted through contact with contaminated feces, was made worse this year by an exceptionally heavy rainy

season that flooded the sprawling shantytowns in Freetown and Conakry, the capitals of Sierra Leone and neighboring Guinea.

In both countries, about two-thirds of the population lack toilets, a potentially lethal threat in the rainy season because of the contamination of the water supply. Doctors Without Borders said there had been nearly twice as many cholera cases so far this year as there were in the same period in 2007 in Sierra Leone and Guinea, when it said the area experienced its last major outbreak.

Already, more than 13,000 people suffering from the disease’s often fatal symptoms — diarrhea, vomiting and severe dehydration — have been admitted to hospitals in the two nations’ capitals, and 250 to 300 have died, Doctors Without Borders said.