Here we go again! We made another mistake. You see, in the last blog we pretty much assumed CDC, or somebody, routinely took a traveler’s temperature if he or she (i) traveled from West Africa, and (ii) deplaned at a U.S. airport. We thought that Mr. Duncan, the Liberian who died of Ebola earlier this week in Dallas[1], had passed such a test before he left the DFW airport and mingled with the rest of us. How naïve! Under the protocols in force when he arrived[2], he was “screened” before he left West Africa, but no physical tests were required or administered when he arrived here.

Now, CDC is of the opinion a person exposed to Ebola is not dangerous to others until he [or she] begins to develop symptoms. The symptoms are a sign that the virus is taking hold, multiplying, and could spread. Nevertheless, anyone exposed to Ebola should avoid commercial air travel. “Persons who have had exposure to Ebola virus should not travel by commercial aircraft because of the risk of developing symptoms in transit and potentially exposing others onboard.”[3] It’s far better that people exposed to Ebola, even those without symptoms, travel by air medical transport, where measures can be taken if symptoms develop.

That seems simple enough. If someone is infected, then he [or she] should come here on a medical flight, equipped to handle Ebola, or not come at all. Then how did Mr. Duncan, and no doubt others that day, come to fly commercial? Well, because in Government, as in life, things are not always what they seem to be. Simple rules are not favored. Instead, these days our CDC distinguishes between levels of exposure, and believes that officials in West Africa know which travelers have been exposed to how much of the disease. Given that on-the-ground knowledge foreign officials will make correct judgments about who should fly.

Let’s see how the reasoning goes. To CDC, people and Ebola fall into one of three categories; they [the people] are at high risk of getting it [the disease]; have some risk of getting it; or have no known exposure to it. So, they should be treated according to their levels of risk.

  • High Risk, with Symptoms. People who are directly exposed to blood or other bodily fluids of Ebola victims are considered to be high risk; if they also have symptoms, especially a fever, they may not fly commercial air. Only medical air transport is authorized for them.[4]
  • High Risk, No Symptoms. If people at high risk have no symptoms, they are placed on “conditional release” and their movements are controlled for 21 days after their “last known potential exposure.” Can they fly commercial air? Theoretically they’re not infectious until they exhibit symptoms, but nevertheless, people on controlled movement “should not travel by commercial conveyances (e.g. airplane, ship, long-distance bus, or train).”[5]
  • Some Risk, with Symptoms. Anyone who has household or other close contact with an Ebola victim is considered to have some risk of exposure; if he also has fever, he may not fly commercial air. Only medical air transport is authorized.[6]
  • Some Risk, No Symptoms. If that person is at some risk but has no symptoms, he may be conditionally released, but his movements should be controlled for 21 days following the last known exposure. Can he fly commercial? Again, theoretically he’s not infectious until he exhibits symptoms; nevertheless, he shouldn’t “travel by commercial conveyances (e.g. airplane, ship, long-distance bus, or train).”[7]
  • No Known Exposure, with Symptoms. This category covers people who visit, or live in a country where there is an Ebola outbreak. A person who has no known, direct exposure to Ebola, but does have a fever, should be watched. Probably he [or she] can fly commercial. “[T]ravel by commercial conveyance is allowed.” Such travelers must “self-monitor for 21 days after leaving the country.”[8]
  • No Known Exposure, No Symptoms. Others, who have no known exposure, and no symptoms, may travel at will.[9]

This is a nice, neat set of classifications, but the trick is to figure out who falls into which ones. How do you do that? Let’s do a thought experiment here, and explore the possibilities. It’s all conjecture, of course. Elemental Zoo Two has no inside information.

Assume that local officials in West Africa follow CDC guidelines. If a traveler has been to a hospital or other medical facility, and has been evaluated, then there are records for the officials to check. Officials can find out if the traveler has high risk of, some risk of, or no “known” exposure to Ebola. But suppose there are no medical records? Does that mean the traveler automatically qualifies as having “no known exposure”?

Probably not. Instead, local officials might want to do an interview. Suppose a traveler says he hasn’t been exposed to Ebola, doesn’t know anybody with it, and stays out of places where people have it. Should the interviewer believe the traveler, or not? If the traveler has Ebola, he might lie just to get out of the country, away from the disease and closer to good medical care. Or if he’s free of the disease, he could be telling the truth. Since there are no corroborating medical records one way or the other, how do local officials make a judgment? Use intuition? Should they accept bribes? None of that sounds very scientific, does it?

If they accept the traveler’s protestations, i.e., that he wasn’t exposed to the disease, but he has fever or other symptoms, they’ll tell him to board his flight and self-monitor for the next 21 days. If he has no fever, etc. they’ll simply wish him bon voyage. If they don’t believe him, or say they don’t, he won’t get on the airplane.

That ends our little experiment and brings us up to this week. As we know, Mr. Duncan, a citizen of Liberia, arrived in Texas on September 20, and soon thereafter developed Ebola. He died a few days ago, and 50 or so people he contacted are being watched. His was the first, domestic case of Ebola in the U.S., and attracted lots of attention.

On Monday, the 6th, our President hosted a meeting of the chiefs and honchos in his Administration who are concerned with Ebola.[10] If you want to see a video of the President’s remarks after that gathering, go to The White House Blog at . Two days later rumors began to circulate[11] to the effect that government employees will now take the temperatures of people arriving at our airports from West Africa. Apparently only 5 airports will be affected. Other details can be found in The New York Times.[12]

So in one sense we were right last time when we said travelers from West Africa are subject to having their temperatures taken at U.S. airports. We were just a little early, or perhaps accidentally prophetic.

Nevertheless, however you characterize it our basic objection back then is still correct. The incubation period for Ebola is commonly thought to be 21 days. So, a person who is infected on a Friday, departs West Africa on Saturday, and arrives here Monday morning, probably won’t show symptoms upon arrival. The traveler has another 18 days to develop symptoms – like fever – and infect our population. Hopefully our domestic health care safety net will catch him [and his contacts] early before he gets really sick. We don’t want a major outbreak here, do we?

So why take the risk? Why not isolate travelers who may be infected until we can conclusively determine their infection status?



[1] See CNN Health, Karimi et al., Thomas Eric Duncan: 6 ways his case differs from other U.S. Ebola cases (October 9, 2014), available at

[2] See CDC, Interim Guidance for Monitoring and Movement of Persons with Ebola Virus Disease Exposure (updated August 22, 2014), available at  Henceforth, this will be cited as Interim Guidance for Monitoring at __.

[3] See CDC, Guidance on Air Medical Transport for Patients with Ebola Virus Disease at G. Transport of an Asymptomatic Exposed Person, available at

[4] See Interim Guidance for Monitoring at Recommendations for Evaluating Exposure Risk to Determine Appropriate Public Health Actions: “If air transport is clinically appropriate and indicated, only air medical transport (no travel on commercial conveyances permitted).”

[5] See CDC, Interim Guidance for Monitoring at Controlled movement.

[6] See CDC, Interim Guidance for Monitoring at Recommendations for Evaluating Exposure Risk to Determine Appropriate Public Health Actions: Again, “[i]f air transport is clinically appropriate and indicated, air medical transport only (no travel on commercial conveyances permitted).”

[7] See CDC, Interim Guidance for Monitoring at Controlled movement.

[8] See Interim Guidance for Monitoring at Recommendations for Evaluating Exposure Risk to Determine Appropriate Public Health Actions: “If movement restrictions and infection control precautions are determined not to be indicated: travel by commercial conveyance is allowed…” Who makes the determination concerning movement restrictions? Probably medical authorities, and I would guess they don’t hang out at airports.

[9] See Interim Guidance for Monitoring at Recommendations for Evaluating Exposure Risk to Determine Appropriate Public Health Actions: “No movement restrictions[;] Travel by commercial conveyance allowed[;] Self-monitor until 21 days after leaving country.”

[10] See The White House Blog, Hudson, The President Meets with Senior Staff to Discuss the U.S. Response to Ebola (October 6, 2014), available at

[11] See CNN Health, Fantz & Cohen, Source: To fight Ebola, U.S. airports to check some travelers’ temperatures (October 8, 2014), available at

[12] See The New York Times, Tavernise, Newly Vigilant, U.S. Will Screen Fliers for Ebola (October 8, 2014), available at There’s also a video explanation on CSPAN from the head of CDC and others, at