Doing the math on Ebola
The president must act to prevent a catastrophic epidemic
Big facts and basic math tell the whole story. We have only begun to see the potential effects of Ebola nationwide. We still have a chance to get this right, but President Obama needs to get active. Big Fact No. 1: A two-in-75 infection rate for medical personal experiencing Ebola exposure is a non-trivial rate. It is significant. Less than a month ago, a single Ebola case had been diagnosed in the United States. That patient complained of symptoms on Sept. 26 and was dead by Oct. 8. In 12 days, he exposed 75 health care workers to the disease, two of whom are now infected.
Ironically, unlike the general public, these nurses had hazmat suits and a Centers for Disease Control (CDC) protocol. One or the other did not work, since the CDC says the nurses were not at fault. Unknown are the numbers of other (as yet uncovered) cases arriving in the United States daily, and those exposed but as yet still undiscovered.
Big Fact No. 2: Incubation for Ebola, as deadly as the bubonic plague, is 21 days. This means that unless someone is quarantined for that time following exposure, public risk remains high. The likelihood that any exposure leads to an infection goes up after 10 days or symptoms. Presently, no quarantine exists for those leaving infected West African countries. No quarantine exists for those entering U.S. airports. Passengers are left unmonitored if they do not evince “a fever” or “look sick.” They are asked to “self-monitor.” Think about this. By the time a person recognizes Ebola symptoms, if they do — and get to a hospital, if they do — it is too late to prevent exposure. They may have been infectious for days.
Big Fact No. 3: Airplanes continue to come to the United States directly and indirectly from infected countries, even as Ebola deaths increase across West Africa. Total numbers of planes coming to the U.S. from West Africa and total passengers arriving via Europe — unknown. Only five U.S. airports taking international flights have any screening — and even then, they have no answer for the 21-day incubation for those infected by not showing symptoms. With no checking at other airports or land crossings, how many may enter? No one knows.
What does this add up to? A daunting health problem. Do the math. If two infections resulted from 75 people being exposed to just one patient, and this group had protective gear, what are the chances that a larger population, without gear, will be infected — and how fast? Imagine that each of the 75 exposed bumped into another 75 persons. We do not know if people can be carriers without becoming infected themselves, or how many of those exposed are not yet showing signs of infection. Already, another 5,625 persons could have been exposed — or, on the other hand, may not. We do not know.
That is, alas, how exponential numbers work — quickly. Imagine the 75:2 ratio of exposures to infections for the next 75. Imagine that no more initial infections are discovered. Of the 5,625 potentially exposed persons, 150 persons could still end up infected over the next 21 days (that is, two in every 75). Maybe all 75 exposed to the first patient were put in isolation before becoming infectious. We can hope so, but we do not know.
Hypothetically, follow the numbers. All this from one infected person treated in a “prepared” hospital. If these 5,625 newly exposed persons all were to become infected, and each then met 75 other persons within 21 days or before diagnosis, most encounters would be without protective gear. At that point, we could see 421,875 exposed Americans — and a sharp rise in the ratio of exposure to infection.
All this could happen within 42 days from Oct. 15, the date on which the second of the two nurses was discovered infected. It probably will not, but once infections multiply, the numbers begin to work against us. That is why we cannot let it happen.
Epidemics happen fast. By third-level contact from a mere 75 people exposed to Ebola, the next leap could theoretically be enormous. At 75 contacts per person, those 421,875 exposed Americans could, within 21 days, potentially infect 31,640,625 additional Americans — one-tenth of the U.S. population. At that point, prevention is more or less academic, and the country would pivot to crisis education, triaging cases, use of primitive treatments and a lot of prayer. Those would be our options.
All this is unlikely, as long as known exposures to Ebola are contained, all contacts found and monitored, then isolated and treated as needed. As long as no one slips through the cracks, protective gear and protocols work and are actually used. As long as the president effectively stops flights from West Africa to the United Stattes with potentially infected persons, judiciously limiting air traffic to United Nations, Red Cross and military planes, as we did in Afghanistan and Iraq. The crisis will not expand if the president stops infected persons from getting to this country through Europe; if he sets up an egress zone from West Africa, effectively quarantining potential passengers for 21 days before flights; if the president provides insurance by quarantine on this side of the Atlantic Ocean for potentially exposed passengers. The epidemic will not take hold if mistakes made are quickly acknowledged, and protocols here fixed.
Finally, it will not happen if Mr. Obama spends real time focused on this issue, instead of seeking to convince Americans not to think about it. However, cranking this disease down depends on a lot of ifs. Given the unforgiving nature of this disease — and of basic exponential math — the president owes all Americans his full attention and considerably more transparency than he has given us. We have a chance to get this right, but the president needs to do the math — and quickly step up. Robert B. Charles is a former assistant secretary of state in the George W. Bush administration.