David Dausey, a Yale-trained epidemiologist who works on controlling pandemics, is dean of the School of Health Professions and Public Health at Mercyhurst University in Erie, Pennsylvania.

Siata Johnson, 23, stands weakly with the help of a relative outside an Ebola treatment center near Monrovia, Liberia. (John Moore/Getty Images)

The United States got its first scare from Ebola last week when Thomas Eric Duncan, a man sick with the virus, traveled from Liberia to Dallas. This man was feared to have been in contact with up to 100 people after he became contagious, all of whom had to be individually evaluated by public health professionals for their exposure risk. Half of these individuals are currently under observation. Nine of them considered to be at highest risk are being checked twice daily for symptoms.

Bodily fluids including vomit spread Ebola, and Duncan — who presented himself to a Dallas hospital only to be misdiagnosed and sent home — vomited on the sidewalk outside of his home. It took days before a properly trained Hazmat crew was sent to the apartment to clean it. The human errors in this single case highlight why it is urgent that we ban all commercial flights from the impacted countries to all non-affected countries until the outbreak is contained. *

Individuals who suspect they have been exposed to Ebola and have the means to travel to the United States have every reason to get on a plane to the United States as soon as possible. There are no direct flights from the three most-affected nations, but passengers can transfer elsewhere, as Duncan did. If they stay in Africa, the probability that they will survive the illness if they have it is quite low. If they make it to the United States, they can expect to receive the best medical care the world can provide, and they will have a much higher probability of survival. So they are motivated to lie about their exposure status (wouldn’t you, in their shoes?) to airlines and public health officials and travel to the United States. *

The incubation period for Ebola is up to 21 days, so a person could get on a plane the day he or she is exposed and spend three weeks in the United States or elsewhere before exhibiting symptoms. Then he or she could potentially infect any number of people here before the disease is properly diagnosed, and they are isolated or quarantined. *

Top U.S. government health officials have spoken strongly against creating a travel ban (though members of Congress increasingly disagree). They say restricting flights will also restrict aid to affected countries and will increase the amount of ongoing unrest. But commercial airlines are not the only ways for the United States to send aid and aid workers. The United States has the most advanced military in the entire world; we can transport people and supplies without commercial carriers.

The Ebola outbreak in West Africa has been compared to a war zone. The disease is now being viewed as a national security threat on par with nuclear weapons. The United States has committed nearly 4,000 troops to impacted countries. It’s time to take security precautions that align with the gravity of the threat. That means doing whatever it takes to keep infected people from coming here.

Correction: Language was added to the paragraphs marked by an asterisk (*) to clarify that there are no direct flights to the United States, though flights stop in other non-affected nations.