It’s a good idea, in theory: Filter out the sick, and let only healthy people board planes. But in practice, airport screenings aren’t very good at keeping disease from crossing borders. And they will be especially ineffective at containing Ebola, according to a new BMJ editorial by a team of researchers at the London School of Hygiene and Tropical Medicine.
Airport screenings wouldn’t have stopped Thomas E. Duncan, for example, from travelling from Liberia to become the first Ebola patient diagnosed in the US, because he didn’t have symptoms yet. They similarly failed to detect SARS passengers travelling to Australia and Canada during the 2003 outbreak.
It comes down to three tools that airport screening staff use to track and contain the sick.
First, the thermal scanner: This tool — an ominously gun-shaped piece of equipment that picks up body temperature — will pick out anyone with a fever. Unless of course, they have popped an aspirin, or, in the case of Thomas Duncan, haven’t yet developed symptoms of the virus.
Plus, most of those who do test positive for a fever won’t have Ebola, and health officials haven’t decided what to do with them yet.
Second, the flight itinerary: Most direct flights from the three countries acutely affected by Ebola — Guinea, Liberia, and Sierra Leone — to the United Kingdom have been discontinued because of Ebola. There are no direct flights from those countries to the US.
People who are still travelling from those countries, then, are using connecting flights from various other cities. That means airport staff will have to thoroughly check passengers’ itineraries to find out where they originated and if they pose a risk, a process that would choke up airport flows and make travel difficult.
Third, the questionnaire: The people who airport staff do identify as posing an Ebola risk will be asked to complete a questionnaire. They will have to answer ‘yes’ or ‘no’ to the following: Have you been in contact with sick people? Have you attended funerals in West Africa? Do you have symptoms of Ebola?
The honest few who answer ‘yes’ will be taken to see a healthcare worker for a diagnosis.
While the screening process isn’t perfect, public officials who support it are under the false premise that it could at least keep a hefty number of people with Ebola from entering their country.
In reality, airport screening would still let 93% of people with Ebola slip through the cracks, because only a handful of those sick with the virus would have symptoms when they arrive at the airport, the researchers estimated. (Their calculations pertain to the UK; because travel times to the US from the affected region are different, the exactly percentage of infected people who would be able to enter the US “unimpeded” would likely vary.)
Several countries have tried using airport screenings to contain diseases in the past. In 2003, Canada tried using the procedure to keep out the SARS epidemic. During the course of the procedure, 700,000 passengers were screened at Canadian airports; close to 2,500 answered yes to the SARS questionnaire. Exactly none were found to have the disease, and the procedure cost Canada $US15 million.
Australia tried the same thing. The country’s airports screened close to 2 million incoming passengers for SARS and found nearly 800 with elevated temperatures. After holding them for additional testing, it turned out that no one had the virus.
“Adopting the policy of ‘enhanced screening’ gives a false sense of reassurance,” wrote the researchers in their editorial. “Our simple calculations show that an entrance screening policy will have no meaningful effect on the risk of importing Ebola into the UK.”
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