Gemineye
Well-known member
[3] Thermal screening: limitations
Date: Fri 15 Aug 2014
From: Jason Cerovac <jcerovac@panix.com> [edited]
Via ProMED Submit Info tab at top of home page
<http://www.promedmail.org>
EVD and Thermal Scanners
------------------------
In reference to [Ebola virus disease - West Africa (127): Guinea,
screening, more 20140815.2691736], Liberian officials using older
contact thermometers and then Mod.JW's comments to use non-contact
thermometers [I was supposing that tympanic (contact) thermometers
were not swabbed with alcohol between passengers, thus carrying a
potential risk. I have been unable to find a video on the internet
showing them in use at an airport. - Mod.JW]:
What is the actual effectiveness of the use of non-contact
thermometers in detecting febrile individuals in an open-air,
non-temperature-controlled environment? What have we learned during
the SARS and H5N1 endemics that could be useful in improving the
screening processes to detect individuals who may be ill?
Experience doesn't equal data; but my experiences are that while
thermal scanning, if done in ideal settings, may be effective; similar
techniques used outside of a temperature and airflow controlled
environment are simply ineffective. The use of contact (temporal,
tympanic) thermometers are necessary in those circumstances, and even
these do not respond well if the environment is overly hot or cold.
Much of the data I could find supports my experience; such as that
published in Eurosurveillance or in Emerging Infectious Diseases over
the past few years [see refs. below].
Used inside of a temperature controlled air terminal, the large and
very expensive thermal imaging devices work well enough; I suspect
more simplistic non-contact devices would do so as well; but the
airports in West Africa, at least those that I have been to, including
Liberia, are not temperature controlled; and individuals have to walk
in from the tarmac. These are not ideal conditions for keeping the
sensitivity high enough to be beneficial.
Furthermore, they are not using thermal imaging devices; instead they
are using a non-contact point and scan device which only measures the
temperature over a small area. Used in the field, at a makeshift
roadside inspection station, and using such non-contact point and scan
devices, the effectiveness would be even less, I suspect.
Are they also using questionnaires? Do they have personnel trained and
experienced in identifying potentially sick travelers? I don't know
that Liberia, or any of the other countries in the region, has the
resources to roll this out in an effective manner. I've visited
hospitals and clinics in Monrovia -- I was unimpressed. Their health
system was in dire straits before the outbreak; it is crumbling under
the pressure of the outbreak; I don't see how they will be able to
manage effective screening checkpoints.
My point in all this is just that I don't think the advice should be
increasing (and placing their hopes of containment) in such screening
checkpoints. Resources are already limited (the daily SitRep from
MOHSW in Liberia remarks on how difficult it is to get bleach and
gloves), don't limit them further. Improve the conditions for the
current contact tracing teams, for the current healthcare workers; but
avoid utilization of resources on methods that are inefficacious. What
good advice can be given to the people in West Africa fighting this
that will actually work to help contain and control the outbreak?
References:
1. Fever Screening at Airports and Imported Dengue; Emerging
Infectious Diseases, Vol. 11, No 3; March 2005
2. Screening for Infectious Disease at International Airports: The
Frankfurt Model; Aviation, Space, and Environmental Medicine, Vol. 80,
No 7; July 2009
3. International travels and fever screening during epidemics: a
literature review on the effectiveness and potential use of
non-contact infrared thermometers; Eurosurveillance, Volume 14, Issue
6, 12 February 2009
4. Nonpharmaceutical Interventions for Pandemic Influenza, National
and Community Measures; WHO Writing Group; published in Emerging
Infectious Diseases, Vol12, No. 1; Jan 2006
5. There's Really No Way To Screen for Ebola at Airports; Defense One;
1 Aug 2014
Limiting the spread of pandemic, zoonotic, and seasonal epidemic
influenza; WHO 2010
6. Controlling infectious disease outbreaks: Lessons from mathmatical
modeling; Journal of Public Health Policy (2009) #30
--
Jason Cerovac
Medical Services Manager for a company with operations in West Africa
<jcerovac@panix.com>
Date: Fri 15 Aug 2014
From: Jason Cerovac <jcerovac@panix.com> [edited]
Via ProMED Submit Info tab at top of home page
<http://www.promedmail.org>
EVD and Thermal Scanners
------------------------
In reference to [Ebola virus disease - West Africa (127): Guinea,
screening, more 20140815.2691736], Liberian officials using older
contact thermometers and then Mod.JW's comments to use non-contact
thermometers [I was supposing that tympanic (contact) thermometers
were not swabbed with alcohol between passengers, thus carrying a
potential risk. I have been unable to find a video on the internet
showing them in use at an airport. - Mod.JW]:
What is the actual effectiveness of the use of non-contact
thermometers in detecting febrile individuals in an open-air,
non-temperature-controlled environment? What have we learned during
the SARS and H5N1 endemics that could be useful in improving the
screening processes to detect individuals who may be ill?
Experience doesn't equal data; but my experiences are that while
thermal scanning, if done in ideal settings, may be effective; similar
techniques used outside of a temperature and airflow controlled
environment are simply ineffective. The use of contact (temporal,
tympanic) thermometers are necessary in those circumstances, and even
these do not respond well if the environment is overly hot or cold.
Much of the data I could find supports my experience; such as that
published in Eurosurveillance or in Emerging Infectious Diseases over
the past few years [see refs. below].
Used inside of a temperature controlled air terminal, the large and
very expensive thermal imaging devices work well enough; I suspect
more simplistic non-contact devices would do so as well; but the
airports in West Africa, at least those that I have been to, including
Liberia, are not temperature controlled; and individuals have to walk
in from the tarmac. These are not ideal conditions for keeping the
sensitivity high enough to be beneficial.
Furthermore, they are not using thermal imaging devices; instead they
are using a non-contact point and scan device which only measures the
temperature over a small area. Used in the field, at a makeshift
roadside inspection station, and using such non-contact point and scan
devices, the effectiveness would be even less, I suspect.
Are they also using questionnaires? Do they have personnel trained and
experienced in identifying potentially sick travelers? I don't know
that Liberia, or any of the other countries in the region, has the
resources to roll this out in an effective manner. I've visited
hospitals and clinics in Monrovia -- I was unimpressed. Their health
system was in dire straits before the outbreak; it is crumbling under
the pressure of the outbreak; I don't see how they will be able to
manage effective screening checkpoints.
My point in all this is just that I don't think the advice should be
increasing (and placing their hopes of containment) in such screening
checkpoints. Resources are already limited (the daily SitRep from
MOHSW in Liberia remarks on how difficult it is to get bleach and
gloves), don't limit them further. Improve the conditions for the
current contact tracing teams, for the current healthcare workers; but
avoid utilization of resources on methods that are inefficacious. What
good advice can be given to the people in West Africa fighting this
that will actually work to help contain and control the outbreak?
References:
1. Fever Screening at Airports and Imported Dengue; Emerging
Infectious Diseases, Vol. 11, No 3; March 2005
2. Screening for Infectious Disease at International Airports: The
Frankfurt Model; Aviation, Space, and Environmental Medicine, Vol. 80,
No 7; July 2009
3. International travels and fever screening during epidemics: a
literature review on the effectiveness and potential use of
non-contact infrared thermometers; Eurosurveillance, Volume 14, Issue
6, 12 February 2009
4. Nonpharmaceutical Interventions for Pandemic Influenza, National
and Community Measures; WHO Writing Group; published in Emerging
Infectious Diseases, Vol12, No. 1; Jan 2006
5. There's Really No Way To Screen for Ebola at Airports; Defense One;
1 Aug 2014
Limiting the spread of pandemic, zoonotic, and seasonal epidemic
influenza; WHO 2010
6. Controlling infectious disease outbreaks: Lessons from mathmatical
modeling; Journal of Public Health Policy (2009) #30
--
Jason Cerovac
Medical Services Manager for a company with operations in West Africa
<jcerovac@panix.com>