BBC News reports a second health worker in t Texas has tested positive for Ebola, health officials say. Both health workers treated Liberian man Thomas Duncan, who died last week after becoming the first person diagnosed with Ebola in the U.S. A local judge said there was a "real possibility" of further cases, and contingencies were being prepared. Meanwhile, the UN's Ebola mission chief says the world is falling behind in the race to contain the virus. The World Health Organization (WHO) says 4,447 people have died from the outbreak, mainly in West Africa. Sierra Leone, Liberia and Guinea have been hardest hit by the outbreak, which began in December 2013 but was confirmed in March. President Barack Obama is due to hold a video conference with British, French, German and Italian leaders to discuss the Ebola crisis later on Wednesday.