The limitation of thermal imaging for mass screening during pandemic outbreaks (fever screening) is the low sensitivity for detecting individuals that are too early in the incubation of the virus. If they are not symptomatic when they are traveling, then there is little chance of identifying them with mass physiological screening.
Thermographic screening at airports and any other locations where the public congregate or travel is targeting individuals who are already symptomatic and likely to be infectious, (coughing, sneezing and the production of mucus causing the fastest spread).
The highest risk for the geographic spread of infection is through travel and ‘seeding’. Thermographically screening travelers has a multi level benefit.
1. Sensitive screening to detect abnormal physiology (hot or cold) will detect a high % of abnormal (which can then be individually evaluated and further tested if necessary) This group will fall into the symptomatic category who will be best detected with a ‘mass’ screening approach (rapid movement through airports etc).
2. Sensitive and targeted screening to detect sub-clinical individuals who may not exhibit symptoms but will show abnormalities days before symptoms evolve.
This will be high risk groups or individuals, traveling from infected areas. The ‘targeted’ protocol will include the controlled testing of each individual (a single thermal image) which will have a greater specificity. The individual will be anterior to the camera, any spectacles or head covering removed and the head and neck will be imaged in a stable environment. (instead of just passing by the IR camera) This group will fall into the asymptomatic category who will be best detected by individual screening checkpoints.
3. Establishing routine fever screening during outbreaks will deter individuals from traveling if they know or suspect that they have any symptoms whatsoever.
This group has the greatest potential to limit the spread through compliance with WHO and other advisory body recommendations (not to travel if you have been exposed to anyone infected or have any symptoms yourself). ‘Nobody wants to be stopped and quarantined’.
Fever Screening stations will not prevent the spread of disease 100% but are an integral part of the effort to limit and contain the outbreak and reduce the number of deaths.