Tuesday, June 17, 2014

WHO: IHR Committee Statement On Thermal Screening For MERS-CoV

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Thermal Scanner – Credit Wikipedia

 

# 8752

 

It sounds logical.

 

Since most viral infections produce fever - and we have the technology able to detect elevated body temperatures (using thermal image scanners) from a distance – that you ought be able to detect, and block, entry of infected individuals at places like airports, borders, and ports.


But like all simple plans designed to deal with complex problems, they tend to look better on paper than they do in reality. 

 

Over the years we’ve looked often at the less-than-sterling performance of thermal scanners in preventing the spread of SARS, pandemic H1N1, and other infectious diseases (most recently in MERS: The Limitations Of Airport Screening).  .

 

The first problem is, the incubation period of many viral diseases runs anywhere from 3 days to 2 weeks.

 

Plenty of time to allow an infected individual to travel through airport screening without symptoms, only to develop them a few days later.  Some people may remain asymptomatic, yet still carry (and potentially spread) the virus.

 

And then there are people who – for a variety of reasons – will take antipyretics (fever reducers) to prevent discovery while traveling.  We saw that during the 2009 pandemic (see Vietnam Discovers Passengers Beating Thermal Scanners). 

 

Added to these, scanners can be foiled by  consumption of hot beverages or alcohol, pregnancy, menstrual period or hormonal treatments.  All of which can increase the external skin temperature and cause a false positive.

 

Inversely, intense perspiration or heavy face make-up can have a cooling effect on the skin temperature which can cause a false negative.

 

Nevertheless, governments around the world tend to roll out these scanners whenever an international infectious disease threat emerges. Likely, because it is reassuring to the public and shows authorities as being proactive against a perceived threat.

 

Despite the fact that evidence for their effectiveness has long been lacking (see Helen Branswell article Airport disease screening rarely worthwhile, study suggests). 

 

Which bring us to a statement, near the bottom of today’s statement from the IHR Emergency Committee on MERS-CoV, 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.

 

Although it isn’t what most people want to hear, there is no technological barrier that can effectively keep infected people from traveling internationally.  It is the price we pay for having an increasingly mobile, and interconnected, society.

 

The takeaway from all of this is that we ignore global healthcare and infectious disease outbreaks – even in the remotest areas of the world – at our own peril. Vast oceans and extended travel times no longer offer us protection.

 

The place to try to stop the next pandemic is not at the gate or border, but in the places around the world where they are likely to emerge.

 

Which makes the funding and support of international public health initiatives, animal health initiatives, and disease surveillance ever so important, no matter where on this globe you happen to live.

1 comment:

Wello Inc - Rik Heller said...

Very interesting article. Your right this problem is very complex. The public loves reassurance but often times what authorities are doing in airports does not prevent the spread. We have researched this topic for some time. For example, with the SARS Singapore epidemic of 2003 they screened for fever at airports and schools with little results. When they screened non-patients at the hospitals 25% of fevered non-patients had SARs. (See Chung SY, Chia F, Leong KK, Kwang YP, Ma S, Lee BW, et al. Mandatory temperature monitoring in schools during SARS. Arch Dis Child 2004;89:738-9.) I wrote about this recently at http://www.welloinc.com/temperature-screening-control/