Coronavirus: Airport screening tests may be ineffective at stopping infected passengers, say experts
Airports around the world might have been relying on an inefficient method to dodge the spread of new coronavirus infections. Screening methods that are only based on checking for symptoms like fever or cough may not succeed at detecting the COVID-19 among travelers, says a report.
This is because some people might pass the symptom-based screening test and still have the virus. What is more, these people might infect others, according to scientists who wrote the report.
"In this effort to evacuate 126 people from Wuhan to Frankfurt, a symptom-based screening process was ineffective in detecting COVID-19 in 2 persons, who later were found to have evidence of the infection in a throat swab," scientists write in their report.
Airport authorities screen for the virus by measuring the body temperature of passengers during the airport security checks. Passengers might also be asked to fill out a questionnaire, asking if they had recently been to Wuhan or if they have had close contact with infected people.
Other researchers also point out the flaws of symptom-based screening. "What we found is that even in the best-case scenario, screening is probably going to miss over half of the people screened. And that's consistent with what we are seeing in the news. Most of the cases in the US were not detectable when they passed through airport screening," writes Dr. Katelyn Gnostic, from the Department of Ecology & Evolution at UChicago, who was not involved in the study.
What does the study say?
The study builds on the gathering screening data on a group of 126 people, predominantly German nationals, who had stayed in Hubei Province before evacuating to Frankfurt, Germany.
"Screening for symptoms and clinical signs of infection was performed before their departure from China. A total of 126 travelers were allowed to board an aircraft operated by the German air force," scientists say.
During the flight, German authorities had isolated those who either had contact with an infected patient or showed signs of infection — 10 of them. Shortly after arrival, all 10 tested negative for the coronavirus infection, says the report.
And the remaining 116 passengers underwent medical tests. Among them, one passenger had an elevated temperature and a cough — but he tested negative too.
The other 115 passengers showed no symptoms or mild symptoms. But when experts collected their throat swabs, they detected the virus in two of them. Of these two, one had a faint rash and sore throat, according to the report.
Even after seven days of hospitalization, these patients had no fever. This, according to the research team, suggests that "shedding of the potentially infectious virus may occur in persons who have no fever and no signs or only minor signs of infection".
This does not mean screening is worthless. "Even though screening isn't effective, it may be possible to stop the global spread of this kind of disease," says Gnostic.
The report has been published in the New England Journal of Medicine.