Sierra Leone leader Ernest Bai Koroma declared a state of emergency on Thursday and cancelled a planned trip to the US-Africa summit as the country struggled to contain the deadly Ebola epidemic. "Extraordinary challenges require extraordinary measures. The Ebola virus disease poses an extraordinary challenge to our nation," the president said in a televised address to the nation. "Consequently... I hereby proclaim a state of public emergency to enable us to take a more robust approach to deal with the Ebola outbreak."