Question

1. Elevated temperature is a common presenting symptom for a number of infectious diseases. List infections caused by viruses other than SARS-CoV in which thermal scanners may be useful tools for mass screening of body temperature in order to delay or avert other public health crises in which widespread transmission of infection is possible. 2. Infrared thermal image scanners were operational in Canada at Vancouver Internation International Airport during part of the SARS outbreak in 2003, and 4,569,759 passengers were actually scanned. An elevated temperature was detected in 1,435 individuals (0.031%). None of them were assessed as having SARS. Approximately 36.3 million people were screened using scanners in Hong Kong in 2003. Of these, only 1,921 had a fever. Forty of these passengers were admitted to a hospital, but none were diagnosed with SARS. From these data, does it appear that mass screening for fever is the most effective means for detecting disease in travelers during an outbreak? Should other "low-tech" approaches be used? Should a combination of both infrared thermal scanners and other approaches be used? Defend your detailed answer.

Answer 1

1. As mentioned in the question, any infectious disease can cause an elevated temperature and could theoretically be detected by thermal scanners. To prevent widespread transmission of infection, the primary focus is to concentrate airborne virus. Influenza virus are the most common category that can cause high fever. Influenza viruses are RNA virus comprising of four species out of which three can cause local epidemic to pandemic:

• Influenza A virus: This virus naturally have an avian origin and hence, it is also called avian flu. Occasionally, viruses are transmitted to other species and may then cause devastating outbreaks in domestic poultry or give rise to human influenza pandemics. This species has been divided into various serotypes which can cause severe fever. The serotypes that have been confirmed in humans are: H1N1, H2N2, H3N2, H5N1, H7N7, H1N2, H9N2, H7N2, H7N3, H10N7, H7N9 and H6N1.
• Influenza B: This virus exclusively infects humans, but is less severe than influenza A
• Influenza C virus: This virus caused local endemic in Yamagata city in Japan in 1996 and 1998.

Other virus that can cause severe airborne infections include:

a) Measles virus: Measles is the most contagious transmissible virus known. Global Measles and Rubella Laboratory Network (GMRLN) data from 2016-2018 suggest that the incidence of measles in general population is decreasing.

b) Ebola virus: It typically occurs in outbreaks in tropical regions of Sub-Saharan Africa.

c) Human coronavirus: Seven strains of human corona virus are known which are human coronavirus 229E (HCoV-229E), human coronavirus OC43 (HCoV-OC43, severe acute respiratory syndrome coronavirus (SARS-CoV), human coronavirus NL63 (HCoV-NL63, New Haven coronavirus), human coronavirus HKU1, Middle East respiratory syndrome-related coronavirus (MERS-CoV or novel corona virus 2012), Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or COVID-19)

d) Rubella or vericella virus: The virus tends to peak during the spring in countries with temperate climates.

e) Variola Virus: The last case of smallpox in the world occurred in an outbreak in the India in 1974.

f) Varicella zoster virus (VZV): Primary varicella occurs in all countries worldwide. In 2015 chickenpox resulted in 6,400 deaths globally.

g) Mumps Virus: Although mild, typically between a few hundred and few thousand cases occur in a year.

2. The primary requisite of mass screening is that the technique used should be non-invassive.Thermal scanning is a noninvasive tool that uses an infrared camera to produce images that show the patterns of heat and blood flow on or near the surface of the body. When a person stands before the cameras, on the computer screens the hotter objects are highlighted with a different colour palette than the rest. These cameras can be calibrated to detect abnormal body temperatures. As with any primary screening tool, this technique has an inherent limitation of inability to detect an infected person who has recently taken an antipyretic or is currently asymptomatic.

The nature of pathogen itself is an important parameter. While thermal screening was not successful in case SARS outbreak in 2003, COVID-19 appears to have a shorter incubation period than SARS which should likely cause a better screening success rate.

An AI based learning approach where potential infected patients are further screened based on their travel record, duration of travel, incubation time of virus, future travel plans, along with thermal screening for infected population, might help in containment of severe airborne infections.

However, there are no guaranteed solutions to ensure infectious diseases are always detected early, before they reach densely populated areas.