听力原文： Polio has been eliminated from Somalia as no case of the disease has been reported for exactly one year, the UN World Health Organization says. The WHO described it as a 'landmark victory' and a testimony to the efforts of more than 10,000 volunteer workers.The country has been riven by war and violence since 1991 and has no central government or detailed medical data. But a WHO spokesman said the UN's network of monitors made it confident in its assessment. Somalia's last case of indigenous polio was in 2002, but it was re-infected three years later with the virus originating from Nigeria.The last case was reported on March 25th. 2007 in central Somalia. The disease, which causes paralysis, has been eliminated in developed nations but persists in parts of India, Nigeria, Afghanistan and Pakistan. What is the main idea of the news item?