The World Health Organization says it is very concerned about an outbreak of cholera in the Sierra Leone capital, Freetown. Authorities say dozens of people have died from the disease in the past two weeks, and the WHO says it is worried it could spread further because of flooding and poor water sanitation in many of Freetown's suburbs.

The World Health Organization says that with cholera, it takes only one case to be considered an outbreak, so it is very concerned by reports of more than 200 cases in Sierra Leone.

A cholera expert with the WHO, Claire-Lise Chaignat, says only the most severe cases are reported, so there could be as many as 1,000 people currently infected with the disease, which can kill quickly if untreated.

"If you have water that is contaminated, then of course if you drink the water, if you use the water you can get contaminated," she explained. "But you can also contaminate food that is being washed by the water. So you get contaminated today, within five days you can die. So in fact, after 24 hours you start to get dehydrated and, in the worst case scenario, you can get the symptoms after one day and then in one to two days you can be dead, even less than five days."

She says that there had been no reported cases of cholera in Sierra Leone in more than four years, and that the WHO is working hard to control the current outbreak.

"If you have all of these ingredients like in a post-war situation, then of course there is a high potential for a huge outbreak," she said. "So that's why it's very critical that the control measures are being put in place in Sierra Leone very quickly."

Sierra Leone is working to rebuild after emerging from a decade-long civil war, which disrupted much of its health care systems and public programs.

According to the director general of medical services in Freetown, Noah Conteh, recent heavy rains have flooded the river in the east of the city. This is the main water supply used by many civilians living in crowded areas of the capital, and Dr. Conteh says the contamination could be spreading from the river.

Dr. Conteh also says poor phone systems are causing delays in receiving information on the spread of the disease, but he says more than two dozen people have died from cholera since the first case was reported two weeks ago.