More than 160 people deemed at risk of catching Ebola in Liberia finished their mandatory surveillance period on Friday, taking the worst affected country a step closer to ending the epidemic. Liberia was the first of West Africa's three most badly hit countries to be declared Ebola-free, once in May and again in September, but each time new cases have mysteriously re-emerged. “We went 21 days and nobody became symptomatic,” said Tolbert Nyenswah, the head of Liberia's Ebola response.