Over 18,000 cases of cholera have been reported in Sierra Leone as of Sept. 17, including 273 deaths, the largest ever cholera outbreak since the 1970s in the west African country, an expert of the World Health Organization (WHO) said Thursday. William Augusto Perea Caro, WHO Control of Epidemic Diseases Coordinator, told reporters that the outbreak started in Feburary in some districts in the coastal area and it went down. When It picked up again in July it mainly affected the Capital city of Freetown. The number is stabilizing currently as number of newly-reported cases dropped to 100 per week from 2,100 at the peak time, and the casualty rate is about 0.5 percent per week now, Perea Caro said. "The case management is working very well," he said. However, the epidemic "is continuing to spread slowly but progressively to the rest of the country", and cases are now reported in 12 out of the 13 districts, he added. He said main causes for this big outbreak are mainly because the increasing migration to Freetown and lack of water and sanitation systems. Besides, "the health infrastructure is extremely extremely weak," he said, adding that cholera has been almost completely taking the country's health resource in the last two months. WHO has established a Cholera Control and Command Center in Sierra Leone, upgraded the routine surveillance system to a daily reporting system, trained more than 1,000 health workers in case management, and help the cholera treatment units in hospitals to be equipped with basic materials. Also working as a partner in cholera control in Sierra Leone, the International Federation of Red Cross and Red Crescent Societies (IFRC) appealed on Thursday 2.62 million Swiss francs (about 2.68 million U.S. dollars) to help fight the outbreak. The funding will help support the Sierra Leone Red Cross Society, which has already deployed more than 700 volunteers to work with communities at risk and provide cholera awareness and hygiene promotion activities, said Amanda McClelland, IFRC Emergency Health Advisor. "Cholera is, and will continue to be a significant disease burden, especially in Africa while inequities in access to basic services exist," she said. Perea Caro also urged to take it as a leverage to improve disease control capacity in the district-level in Sierra Leone.