A security personnel checks the temperature of passengers arriving at the Shanghai Pudong International Airport in Shanghai on February 4, 2020. - The new coronavirus that emerged in a Chinese market at the end of last year has killed at least 425 people and spread around the world. The latest figures from China show there are more than 20,400 people infected in the country. Outside mainland China, there have been more than 150 infections reported in around two dozen places. There have also been two deaths, in the Philippines and Hong Kong. (Photo by NOEL CELIS / AFP) (Photo by NOEL CELIS/AFP via Getty Images)
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A security personnel checks the temperature of passengers arriving at the Shanghai Pudong International Airport in Shanghai on February 4, 2020. - The new coronavirus that emerged in a Chinese market at the end of last year has killed at least 425 people and spread around the world. The latest figures from China show there are more than 20,400 people infected in the country. Outside mainland China, there have been more than 150 infections reported in around two dozen places. There have also been two deaths, in the Philippines and Hong Kong. (Photo by NOEL CELIS / AFP) (Photo by NOEL CELIS/AFP via Getty Images)
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CNN  — 

One of the enduring images of the current coronavirus outbreak is a space-age looking thermometer pointed at an airplane passenger.

Eleven airports in the United States are using these temperature checks as part of expanded screening for novel coronavirus, and those measures might seem reassuring. If someone doesn’t have a fever, it seems like they’re fine – right?

Not so fast.