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A Primer on the Deadly Math of Ebola

Liberian Red Cross health workers wearing protective suits carry the body of a victim of the Ebola virus in Monrovia on Sept. 12
Liberian Red Cross health workers wearing protective suits carry the body of a victim of the Ebola virus in Monrovia on Sept. 12Photograph by Zoom Dosso/AFP via Getty Images

If the Ebola virus continued to tear through the world’s population at the rate it has done recently in West Africa, all hell would break loose. The U.S. Centers for Disease Control and Prevention estimated on Sept. 26 that cases in Liberia and Sierra Leone were doubling every 20 days. Hypothetically speaking, if the Ebola outbreak continued to spread at that same pace, which it won’t, the number of cases would surpass 1 million by January, 100 million by June, and 1 billion by August, before infecting the entire world population sometime next fall.

To repeat, this is not going to happen. The point of running out the figures on unconstrained growth is to shed light on what things will probably happen in the coming weeks and months that will constrain Ebola, bending its growth curve downward and eventually causing this outbreak to end. These range from better care to more effective isolation to the simple fact that people who are exposed but don’t die will build up immunity. “It’s going to stop growing. What we can’t say yet is when,” says Jeffrey Shaman, an associate professor of environmental health sciences at Columbia University’s Mailman School of Public Health.