Are the new Ebola screening measures likely to be effective?

The US Centers for Disease Control (CDC), along with US Customs and Border Protection (CBP), announced a series of new screening measures on Oct. 8 at selected US airports. These measures, which will focus on travelers arriving from the west African nations of Liberia, Guinea, and Sierra Leone, the three nations most affected by the latest Ebola outbreak.

These new screening measures will be at five airports: New York’s JFK and Newark airports, Washington Dulles, Chicago O’Hare, and Atlanta. The first airport to begin screening will be JFK on October 11th, and the enhanced entry screening at the other four airports by the end of the following week.

Why these five airports? While the CDC admits that no procedure will completely eliminate the risk of an Ebola outbreak in the US, These new screening measures will be at five airports: New York’s JFK and Newark airports, Washington Dulles, Chicago O’Hare, and Atlanta. According to the CDC, these five airports represent the US entry point for the first airport to begin screening will be JFK on October 11th, and the enhanced entry screening at the other four airports by the end of the following week.

Why these five airports? According to the CDC, these five airports receive over 94 percent of travelers from the Ebola-affected nations of Guinea, Liberia, and Sierra Leone. From August 2013 to July 2014, with JFK alone accounting for almost half the arrivals

What are the new procedures? Travelers from these three countries, who would have already gone through exit screening protocols in the affected West African countries, will face the following process:

  • Travelers from Guinea, Liberia, and Sierra Leone will be escorted by CBP to an area of the airport set aside for screening.
  • They will be observed them for signs of illness and asked a series of health and Ebola exposure questions.
  • They will also have their temperature taken by a non-contact thermometer.
  • If the travelers have fever, symptoms or if the health questionnaire reveals possible Ebola exposure, they will be evaluated by a CDC quarantine station public health officer, and if necessary referred to the appropriate public health authority.
  • Travelers from these countries who are not Ebola-like symptoms exhibiting symptoms and who have no known history of exposure will receive health information for self-monitoring and will be allowed to enter the country.

How effective has exit screening been?
According to the CDC, since exit screening began about two months ago in Liberia, Guinea, and Sierra Leone, 36,000 people were screened and 77 people were kept from boarding a flight.

None of these 77 passengers were diagnosed with Ebola. However, at least one passenger who was infected with Ebola, but who was apparently not exhibiting any Ebola symptoms, was able to depart Liberia on September 19th, and flew to the US through Washington Dulles airport and then onward to Dallas, TX. This passenger,Thomas Eric Duncan later fell ill and died from Ebola.

How effective will this new entry screening process be?
In order for this screening process to identify passengers who are infected with Ebola, passengers must either be being both able and willing to provide accurate information on their Ebola exposure, or the passenger has to be exhibiting a fever or other symptom associated with Ebola.

Perhaps most importantly, in order to be even screened by this procedure, a passenger must be on a flight that comes directly from one of the three affected countries, and they must enter into one of the five airports that are part of the new screening program.

This means the roughly 6% of passengers who fly directly from the affected countries into another airport are not screened at all. However, there is a potentially much larger pool of passengers who will not be screened or who will not be identified by the proposed screening process, including passengers in the following categories:

  • Not flying directly from the three targeted countries, for example having a layover of one or more days before flying onward to the US.
  • Persons exposed to Ebola, who are not showing any symptoms, and who are either not aware of their exposure or who are not truthful about their exposure.
  • Either exposed to or infected by the Ebola virus, and possibly even showing Ebola-related symptoms, but who are not flying from the three targeted countries.
  • Entering the US by sea or through a land border.

Why make the effort if it will not be 100% effective?
The goal of these new procedures is the find and treat any passenger infected with Ebola upon arrival in the US. Clearly, these new procedures were not designed to screen every passenger entering the US, or even every passenger who is from a country that has had one or more reported Ebola cases (which include Nigeria, Senegal, and Spain).

Like many risk-reduction procedures, they will reduce the likelihood of that an Ebola-infected passenger will enter the US. However, given that passengers who are not exhibiting symptoms can easily escape notice, and that many categories of people entering the US will not be screened at all, it is quite likely that these new CDC and CBP procedures will at best be only somewhat effective and preventing an infected person from entering the US.

Additional information
AirSafe.com Ebola overview
How one Ebola-infected passenger made it to the US
CDC fact sheet on new screening procedures