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 [...]

Released May 1, 2009
 
As concern continues to mount about the spread of the swine flu globally, airport authorities are responding by using digital thermal imaging technology to scan passengers. Thermal imaging can detect elevated body temperature, one of the signs of the virus N1H1 (swine flu).
 
“Medical thermal imaging at airports and any other locations where [...]