WASHINGTON — “Of all the things that could kill more than 10 million people around the world,” writes philanthropist Bill Gates in The New England Journal of Medicine, “the most likely is an epidemic stemming from either natural causes or bioterrorism.”

Beginning with this blunt and clinical assessment, we are given a detailed picture of the specter that haunts Gates’ nightmares:  the emergence of a highly-infectious virus that would spawn global panic, overwhelm the supply of medical commodities, set off a desperate technological race against death, reduce global wealth by trillions of dollars and fill millions of graves.

The genetic mutation that would lead to this outcome is not likely to occur tomorrow. It is likely to occur as tomorrows gather into decades. The Spanish flu of 1918 infected about a third of the world’s population and caused 50 million deaths. An elevated temperature in the morning could mean death by dinnertime.  The AIDS virus, in contrast, kills slowly and spreads without obvious symptoms — a different but highly effective evolutionary strategy of mass slaughter. About 40 million people have died from AIDS.

Like others in his field, Gates describes the Ebola outbreak as “a wake-up call.” This is fair, with the caveat that the crisis is not over. Liberia has demonstrated (remarkably, heroically) that the goal of zero new infections is achievable. Sierra Leone, however, is still seeing transmissions occur from unsafe burial practices. In remote parts of Guinea, traditional healers still resist basic prevention methods (while sometimes accusing foreigners of importing the disease).

But this killer, even after taking about 10,000 victims, is not the mass murderer that Gates is warning against. Ebola is spread through bodily fluids by people who are highly symptomatic — mainly putting families and caregivers at risk. The disease originated in three small countries with a limited number of travelers to the U.S. And these countries welcomed outside intervention. (Imagine trying to send the 101st Airborne Division to respond to a disease outbreak in Islamabad.)

What Gates calls “the next epidemic” is likely to be an airborne virus, turning markets or airplanes — really any congregation of breathing humans — into places of mass transmission. Modern travel would hasten the globalization of death. Following the Ebola crisis, we know one thing with complete certainty: The world would be utterly unprepared for an outbreak 100 times as large.

The first and foundational layer of pandemic preparedness is the disease surveillance system in developing countries. During a recent trip, I visited Tanzania’s national lab, which provides test results for 200 health sites and tracks infectious diseases such as measles, rubella, HIV/AIDS and flu. The lab is in the process of upgrading from a BSL-2 facility to a BSL-3 — allowing it to test for Ebola rather than sending samples to Nairobi (which would cut potentially vital days off the process). The facility would not exist without funding from the President’s Emergency Plan for AIDS Relief (PEPFAR) and the World Bank, as well as the training of technicians by the Centers for Disease Control and Prevention.

The next time a politician sneers at “foreign aid,” substitute the words “disease surveillance” and see if his or her statement still makes sense. Many developing countries lack even the minimal capability to identify outbreaks before they become epidemics. Filling those gaps is one of the goals of President Obama’s essential Global Health Security Agenda, designed to strengthen surveillance capacity in 30 countries comprising 4 billion people.

The second layer of preparedness is emergency response — the ability, on a moment’s notice, to provide mass logistics and command-and-control in the midst of chaos. This is a very rare global capability — currently possessed by the U.S. military, NATO, and pretty much no one else.

“From the movies,” former White House Ebola czar Ron Klain told me, “you’d think there was some rapid response force of 5,000 guys in yellow biohazard suits ready to deploy. It is not true.” The urgent questions are how and where such a capacity might be created. The United Nations and the World Health Organization won’t be ready to play this role anytime soon. Only the G-7 nations would seem to have the ability, wealth and inclination.

All this raises questions of leadership and global governance. If the worst happens, would anyone be in charge? The day before the next epidemic, this will seem a secondary matter. The day after, there will be no other issue.