MONROVIA, Liberia — In my career as a medical doctor and global health policy maker, I have been in the middle of monumental struggles, including fights to make treatment accessible in the developing world for those living with H.I.V./AIDS as well as multi-drug resistant tuberculosis. But the Ebola epidemic is the worst I’ve ever seen.

More than 11 months into the crisis, thousands of people are dead and more than 17,000 have been infected. The virus kills quickly, spreads fear even faster, alters human relationships, devastates economies and threatens to cruelly extinguish hope in three fragile countries that were on the rebound after years of misery. No other modern epidemic has been so destructive so fast.

Recently, the regional response to the Ebola epidemic has been extremely effective in slowing its spread. Presidents Alpha Condé of Guinea, Ellen Johnson Sirleaf of Liberia and Ernest Bai Koroma of Sierra Leone have shown strong resolve and determined political will in battling the virus. I recently spent two days in those countries and saw first-hand that the situation today is far better than it was a month ago because of national and international efforts.

But we are not yet on the path to end the epidemic. These three countries and the world must now shift the focus of their strategy with one goal in mind: zero Ebola cases. While each country faces different challenges in reaching this destination, there are common principles that can guide them. Here are five steps the world must take together.