Josh Michaud, associate director for Global Health Policy at the Kaiser Family Foundation, compares airport screening to seeking a needle in a haystack.

“If the goal is to identify new cases of an emerging disease like the novel coronavirus, then airport screenings have been historically poor methods to identify new cases based off of studies,” Michaud said.

He points to a report noting the failure of airport screenings in Canada to detect a single case of severe acute respiratory syndrome, or SARS. In 2003 that disease killed 774 people, including 43 Canadians. Both SARS and the new Chinese bug are coronaviruses.

Michaud also referred to a study criticizing the effectiveness of using temperature scanners at U.S. airports to detect infectious disease. The study’s authors say thermometers offer passengers emotional reassurance, a signal that government is doing something in response to the outbreak, even if they don’t provide medically sound information.

Detecting a rare disease among thousands or potentially millions of passengers is very difficult, Michaud said. For example, the screening could easily miss infected people without symptoms. He would rather see more resources allocated to places like Taiwan or Thailand that are experiencing new cases.

“Make sure that those systems are functioning well,” Michaud said, “that the providers are well-educated, that they know what to do and how to report those cases.”

This view has not dissuaded authorities from checking people where they can. Bei Bei Tong, a young woman wearing gold spectacles and bright red lipstick, arrived recently at SFO from Wuhan. Like most of the arriving passengers, she’s visiting the Bay Area for the Lunar New Year celebrations that begin this weekend.

Tong says Chinese health officials checked her temperature before she boarded the plane in Wuhan. When she landed, U.S. health officials checked her temperature again and scanned a health questionnaire that asked if she’d coughed, felt feverish or experienced other signs of illness. If a passenger’s temperature is above 100 F, screeners will pull that person aside for extra tests like a chest x-ray beyond the airport. As of Wednesday evening, public health screeners at SFO had not flagged any passengers for more testing.

Despite multiple screenings before she cleared U.S. Customs, Tong said she’s too excited to worry about getting sick. She was on her first trip outside of China, and she believes her home country has its citizens’ best interests in mind.

“I believe my government,” Tong said. “They do many things to protect ourselves.”