Airport screening for viruses is back, despite post-sars study that found it didn’t work
TORONTO – In 2005, a federal government scientist named Theresa Tam coauthored a revealing study that found Canada had spent $7.5 million on screening air passengers for SARS, and achieved exactly nothing.
Not a single case turned up among over one million travellers vetted, Tam and colleagues reported. The disease was so relatively rare, the odds of finding a passenger ill with it were negligible, they concluded. The researchers suggested resources be focused elsewhere.
But more than 15 years later, the government is again implementing an airport screening system — this time for the new Wuhan coronavirus — overseen by the Public Health Agency of Canada that Tam now heads.
That system is already generating controversy, after Canada’s first confirmed case of the virus — a man coming back from China — had passed through Toronto’s Pearson airport essentially undetected.
But Tam’s 2005 study and other evidence call into question whether such measures ever serve much purpose, despite their expense.
“It really is like looking for a needle in a haystack, and sometimes that needle is even camouflaged,” said Josh Michaud, a global-health policy expert at the Kaiser Family Foundation in Washington, D.C. “The question becomes: Is it worth the time, effort and money, especially if the resources being put to border screening are being taken from somewhere else.”
The World Health Organization says that entry screening “offers little benefit, while requiring considerable resources.”
Still, Michaud said in an interview there might be some value to the practice, noting that Thailand has discovered three cases of the new illness, referred to as 2019-ncov, through airport checks.
Tam clarified Monday exactly what happened when Canada’s first case and his wife passed through Pearson on Jan. 22, contradicting earlier suggestions that the couple had withheld pertinent information.
The man, now in hospital in Toronto, was interviewed by a Canada Border Services Agency officer after he got off a flight from Guangzhou, China at Pearson, said Tam, Canada’s chief medical health officer.
He had indicated on an electronic questionnaire that he had been in Wuhan, she told a telephone news conference.
The traveler also disclosed that he had a “mild cough,” but was allowed to leave freely, equipped with a form explaining what he ought to do should his symptoms get worse, Tam said. His family called 911 the next day when his symptoms worsened, and he was taken to hospital using appropriate protections.
“That was a very reasonable approach,” she said of what occurred at the airport. “There was really no obvious illness … Most of the symptoms developed after entry.”
The man’s wife has now tested positive for the disease, though was not feeling ill as of Monday, said Toronto’s medical officer of health, Dr. Eileen de Villa. Her publichealth department is working to contact everyone on the plane — China Southern Airlines flight CZ311 — who sat within three rows of the couple.
Canada’s enhanced screening for passengers on flights from China to Toronto, Montreal and Vancouver was implemented Jan. 22, the same day the pair arrived.
Signs now advise passengers to report any flu-like symptoms, while electronic kiosks ask if they have been to the Wuhan area recently or are experiencing symptoms.
Public Health Agency personnel have been newly assigned to the airports. Border officers are generally supposed to refer travelers with infectious-disease symptoms to those public-health officials.
The SARS screening program in 2003 was similar, requiring passengers to fill out forms that asked if they had a fever, experienced certain symptoms or had had contact with a SARS sufferer. If they circled any of those, they were referred to a nurse for indepth questioning.
More than 1.1 million passengers were screened from March to July 1983 — both entering and leaving Canada — and zero cases were discovered. The relatively short period of time that people spend in airports and on flights makes catching them as they suffer from infectious disease “challenging,” said the researchers, all from the PHAC.
“Rather than investing in airport screening measures to detect rare infectious diseases, investments should be used to strengthen screening and infection control capacities at points of entry into the healthcare system,” said their paper in the journal Emerging Infectious Disease.
A 2009 U.S. study concluded that scanners designed to detect fever in passengers are also mostly ineffective.
Tam seemed to reflect such findings Monday, stressing that vetting travelers as they enter Canada is no guarantee of preventing the import of cases.
The screening that takes place in hospitals, clinics and other health-care facilities is just as important as a way of identifying the new virus in Canada, she said.
Some experts, though, still argue strongly in favour of airport screening.
Travelers who have been to China should be questioned, and followed by health authorities after they enter the country, infectious-disease specialist Aileen Marty told the CBC.