Thermal Scanner – Credit Wikipedia
For every complex problem there is an answer that is clear, simple, and wrong. - H. L. Mencken
Over the years I’ve probably written about the futility of trying to prevent entry of infectious diseases into a country by airport or border screening at least a dozen times. A few recent examples include:
It is not the message that most people want to hear. But the truth is we possess no technology that can reliably detect someone who is infected – but not yet overtly symptomatic – with an infectious disease like influenza, MERS, or Ebola. With luck, you might delay entry of an emerging pandemic virus by a few days or weeks, but even that may be overly optimistic.
In December of 2009, in Travel-Associated H1N1 Influenza in Singapore, I wrote about a a study in the CDC’s EID Journal entitled: Epidemiology of travel-associated pandemic (H1N1) 2009 infection in 116 patients, Singapore that determined that airport thermal scanners detected only 12% of travel-associated flu, and that many travelers boarded flights despite already experiencing symptoms.
While fever scans tend to reassure the public, they are easily fooled (see Vietnam Discovers Passengers Beating Thermal Scanners), and non-specific – resulting in a lot of false alarms. Last June, in WHO: IHR Committee Statement On Thermal Screening For MERS-CoV), we saw the following opinion regarding the effectiveness of thermal screening at airports and borders.
Finally, the Committee indicated that there was no solid information to support the use of thermal screening as a means to stop or slow the entry of MERS-CoV infections, and that resources for supporting such screening could be better used to strengthen surveillance, infection control and prevention or other effective public health measures.
Yesterday the CDC’s EID Journal posted a detailed perspective, which looks back over earlier attempts with SARS and the 2009 H1N1 influenza virus to interdict infected arrivals through screening. Follow the link to read their reasoning in its entirety.
Volume 21, Number 2—February 2015
Linda A. Selvey , Catarina Antão, and Robert Hall
Author affiliations: Curtin University, Perth, Western Australia, Australia (L.A. Selvey, C. Antão); Monash University, Melbourne, Victoria, Australia (R. Hall)
In response to the severe acute respiratory syndrome (SARS) pandemic of 2003 and the influenza pandemic of 2009, many countries instituted border measures as a means of stopping or slowing the spread of disease. The measures, usually consisting of a combination of border entry/exit screening, quarantine, isolation, and communications, were resource intensive, and modeling and observational studies indicate that border screening is not effective at detecting infectious persons. Moreover, border screening has high opportunity costs, financially and in terms of the use of scarce public health staff resources during a time of high need. We discuss the border-screening experiences with SARS and influenza and propose an approach to decision-making for future pandemics. We conclude that outbreak-associated communications for travelers at border entry points, together with effective communication with clinicians and more effective disease control measures in the community, may be a more effective approach to the international control of communicable diseases.
Historically, most attempts at border screening have been ineffectual, as demonstrated by the pandemic spread of SARS and influenza A(H1N1)pdm09 to many countries despite the use of border screening. Modeling and observational studies have indicated that border screening is likely to be unsuccessful in preventing or delaying the entry of such diseases into a country. Border screening generally has high opportunity costs, both financially and in terms of the use of scarce public health staff resources at a time of high need. We conclude that border screening should not be used. Instead, the less costly measure of providing information to arriving travelers is recommended, together with effective communication with local clinicians and more effective disease control measures in the community.
Politically, and in terms of reassuring the public, the screening of passenger arriving at airports and other points of entry probably has some benefits. And it can provide an opportunity to educate arrivals about symptoms, and what to do should they fall ill.
But practically, as an effective way to keep an emerging virus out of a country, studies continue to show just how unlikely that outcome really is.