Over the last several months, scientists at the Food and Drug Administration and World Health Organization have done an excellent job of educating the public about Ebola. They have provided a great deal of factual information and succeeded in preventing widespread overreaction and panic in the U.S. and other developed countries. They emphasized the fact that Ebola is not spread through respiration, tried to reassure the public that air travel remains safe, and they have outlined plans on how to deal with the infection, plans which recognize the biological behavior of the disease.

However, physicians who have been in practice for many years regarded with skepticism some earlier comments from various public health officials and even President Obama that the odds of an Ebola outbreak in the United States are "extremely low." Medicine can be a very humbling profession, and after more than 30 years of practicing infectious-disease medicine, I have learned that the "unanticipated" happens all too often, especially where microbes are involved. Over the last two weeks, the rosy scenarios painted by the Centers for Disease Control have lost their glow and started to unravel.

The fact that Ebola is transmitted by bodily fluids and not by the respiratory route provides no guarantee that there won't be an outbreak in the U.S. or Europe. Consider other non-airborne diseases. Polio was responsible for tens of thousands of deaths in the U.S. In 1952, two years before a successful vaccination program arrested it, there were over 60,000 cases reported. Cholera was responsible for hundreds of thousands of cases in the U.S., although at a time when sanitation practices were substandard. Vaccines and antibiotics have largely eliminated typhoid in this country, but prior to their availability, it caused considerable morbidity and mortality. Obviously, there are major epidemiological differences between all these infections, but none of them are generally spread by respiratory droplet—yet all of them have been responsible for serious or even catastrophic outbreaks. 

Now, predictably, we have seen Ebola cases developing in the U.S. and Europe. There is a real possibility that the numbers will proliferate more rapidly than expected. Here are four problems that could contribute to this:

1) Emergency rooms are frequently too busy to establish a correct diagnosis. This certainly has been true with other infectious diseases. (I frequently see patients with sepsis sent out of the ER, only to return the next day.) Sick patients may stay in the waiting room for considerable periods of time, and be placed in rooms with other patients before a diagnosis of Ebola is entertained. The problem that arose at the Dallas hospital ER will likely be repeated many times. And first responders, like paramedics, often don't have the luxury to triage patients properly before administering care. Furthermore, most community hospitals are not prepared to handle Ebola patients, and the required preparations are much more daunting than most people understand.  The U.S. healthcare system is capable of absorbing and treating some Ebola cases, but outbreaks, when they occur, will likely be centered in one community or another, so on a local level there may not be enough intensive-care-unit beds or isolation rooms or personnel to handle a moderate-sized cluster of patients. If this occurs during an influenza outbreak, the problem will be magnified.  

2) Breaks in infection control policies within hospitals are extremely common. At Texas Presbyterian Hospital in Dallas, for example, the patient was placed in a room with several other patients, and the staff did not use the indicated protective gear. This could have happened at any hospital in the country. 

3) Although contact tracing is relatively easy with one patient and one generation of contacts, it can become daunting or even impossible if dozens of patients and three generations of contacts are involved. Some contacts will simply never be recognized until after they become ill. Given the long incubation period of Ebola—up to 21 days—it is not unreasonable to think this will happen. And Wednesday we learned that one of the nurses caring for Duncan who was supposed to be under "observation" was able to board a plane for Cleveland. It is not clear how completely the other exposed individuals adhered to their isolation, but when dealing with such large numbers of exposed individuals, there will likely be violations which could potentially result in further transmission. 

4) Although it has frequently been stated that patients are not contagious before they are sick, I wonder how absolute this is. Clearly they are infected with the virus before they are sick. They are not shedding virus because they are not vomiting or having diarrhea, but can a patient spread it sexually before they are symptomatic? Or through a nosebleed? 

Until a vaccine or effective antibiotics become available, it may be very difficult to stop this outbreak in the U.S. now that it is here. There are ways to slow it down, however, which will provide more time to develop that medicine and to prepare hospitals to handle more cases. Quarantine is one tool that has been successfully employed in the past; currently, it is being underutilized. I would maintain that every individual traveling here from a country with an active outbreak—currently Liberia, Sierra Leone, Guinea, and Nigeria—should be quarantined. 

This obviously will result in considerable inconvenience and some expense, and in this respect I realize that it sounds draconian. But the fact is, it will prevent most importation of the disease. If the quarantine could be established prior to travel, then virtually no cases would be imported from West Africa. Ultimately, it will diminish the total number of people being quarantined and being tracked, since there will be fewer contacts and less transmission. And at the present time, with only 150 people trying to enter the country from West Africa, it is still a feasible strategy. Of course, this strategy becomes less powerful if it is not adopted worldwide, before an outbreak occurs first in one new country, then another. Note that I am not advocating travel bans. It is hard to disagree with Dr. Anthony Fauci, the National Institutes of Health director of infectious diseases, and CDC Director Thomas Frieden when they point out the necessity of engaging the outbreak at its source, and being able to provide material support to the affected regions. 

President Obama has stated that we have "little room for error" in dealing with Ebola. But the airport screenings that have gone into effect will miss a large percentage of infected individuals, perhaps the majority of them. Relying on these screenings to prevent importation of Ebola is a huge error. A much more rigorous program is required to prevent, or at least delay, a possible catastrophe. Ultimately, the development of an effective vaccine will make these measures unnecessary; the CDC and WHO's support in expediting the development of vaccines is enormously positive. In the meantime, we need to ask ourselves these questions: Even if there is only a 2 percent chance of an epidemic developing in the U.S., should we be relying on half-measures to prevent it? Should we accept the possibility that we are allowing new cases of Ebola to enter the country every day when we have the ability to prevent it?