It's also true that scanners don't catch non-feverish carriers. But alternative methods don't, either. Right now, U.S. airports are counting on Customs and Border Protection officers to spot visible symptoms. According to Homeland Security Secretary Janet Napolitano:
All persons entering the United States from a location of human infection of swine flu will be processed through all appropriate CBP protocols. Right now those are passive. That means that they're looking for people who—asking about, are you sick, have you been sick, and the like; and if so, then they can be referred over for further examination. Travelers who do present with symptoms, if and when encountered, will be isolated per established rules.
Looking for symptoms? Asking people whether they're sick? Come on. At least a heat scanner measures something quantifiable and catches more than the eye can see.
Skeptics at the WHO say border screening is disruptive. But scanners are far more efficient and less disruptive than labor-intensive alternatives. Earlier this week, Japan reported that officials, doctors, and nurses in that country were boarding flights to examine arriving passengers for flu symptoms. By comparison, the latest generation of thermal imagers can instantly scan travelers as they pass by.
If you think heat is a bad proxy for flu infection, ask yourself whether it's worse than nationality. Travel companies are canceling flights to Mexico. Today, Japan began denying visas to Mexicans on arrival. Governments and businesses want an easy way to identify, segregate, and scrutinize the people most likely to be carriers. Which group would you rather they target? People with excess body heat? Or Mexicans?
SARS and bird flu weren't the last plagues to spread across our planet. This flu won't be the last, either. Fortunately, all these viruses have one thing in common: fever. For now, late as it is, that heat signature is our best shot at catching them. Let's use it.